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Title: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 17, 2008, 01:26:38 AM Fixed: AES JAMMA system
Symptom: Would only play the supplied Puzzle De Pon cartridge. This was a strangely modified home game system. It had a custom BIOS chip and an added on chip that was used to add in a test switch and game credits. It also had an external audio amplifier board and a JAMMA edge connector/wires soldered in to allow it to be played in an arcade. Pulled the added-on 74LS245 IC, wiring, test switch, and custom BIOS chip. Erased and reprogrammed the custom BIOS chip with UniBIOS code. Resoldered cracked solder joints on the external audio amplifier. System will no longer take quarters or have an arcade style test switch with coin reporting,etc, but will now play all AES games as requested by the owner. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 17, 2008, 01:26:53 AM Subject: Troubleshooting vertical lines on the MV6 6-slot system
Do you have vertical lines on the screen either on the moving foreground objects or background objects on your 6 slot board? On the 6 slot board there are a bunch of 74LS251 8 to 1 data selector ICs. The ICs nearest slot 6 are for the foreground objects and the ICs nearest slot 1 are for the background objects. The easiest way to check these chips for the bad one is to put a test cart in slot 5 and flip DIP switch 8 to pause the screen where you can see the problem images on screen. Next take the logic probe and check pin 15 of each 74LS251. Look for the IC with no signals on that pin. If you find one without a signal then check the trace between the slot and that pin. Not fixed? Next check pin 4 of each 74LS251 for data output. If one is missing then replace the IC. Still not fixed? Next take the logic probe and put it on pin 15 of each 74LS251. Slide the tip over to where it momentarily shorts between pin 15 and 16. Look at the screen for lines. See lines pop up? That's not the chip you are looking for. Finally find one that doesn't pop up any extra lines when you short it across? OK. That's the data line that is the problem. Follow pin 4 of that chip and find where it connects to go to the bottom board. Can't find where it goes to the connector? Check a neighboring 74LS251 IC and see where it goes. If you can find it then check for a bad trace between the suspect data line on pin 4 and the connector to the bottom board and patch it. Still not it? Check the connection between the top and bottom board. If there is no signal then desolder the connector, disassemble it, pull out the offending connector piece, clean it, reassemble, and resolder it back in place. Test it. Still no? Follow that trace to the chip it goes to and if the trace is good then replace the chip. If that doesn't do it then call a priest and have the board exorcised. Enjoy! Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 17, 2008, 01:27:08 AM Model: MVS MV-4 (4 slot)
Symptom: Missing background graphics There's a 74LS138 on the top board. It's a 3 to 8 decoder. It's used to enable the slot wanted. Not part of the repair, but just wanted to doc it on the forum. Also, there are a LOT of 74LS244 buffers & 74LS245 latches on the board. Each one is hooked together with the neighboring chip that is doing the same function on each of the different slots. In other words, each cartridge slot has multiple buffers and latches. Each latch for specific connections (program data lines 0-8, for example) on the cartridge slot has their board side connections (not cartridge side connections) tied together to the connectors that take the signal to the bottom board. Now, on to the repair: Test Cart used: Shock Troopers, 2nd Squad. This top board had a totally white screen with the exception of the "insert coin" words in the center and the "credit 0" at the bottom right and even that text was mispelled... Used a logic probe to check each and every chip for input and output logic levels. Found a 74LS244 next to slot 4 that had incorrect levels for input vs. output. In tracing the pins on the chips I discovered that there is a chip doing the same thing for each of the slots and they are all tied together. That makes 4 video ROM buffers - one for each slot - all tied together when the connect to the bottom board. Why does it matter that they are tied together? Well, when one shorts it tends to draw excessive current through the others and takes them out too. Replaced the 74LS244 chips at locations N4, J4, E4, and A4 to fix. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 17, 2008, 01:27:22 AM Model: MVS MV-4
Symptom: Cartridges do not work. Crosshatch pattern is all you get on the screen, no matter what slot. Unusual in that the problem follows the top board when swapping boards out. Resolution: There is a 74F138, 3 to 8 decoder, at position A2 that determines which slot is active. Fixed broken trace on one of the 3 enable lines to allow the system to switch the slots and access the cartridges. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 17, 2008, 01:27:34 AM Model: MVS MV-4
Symptom: Vertical lines in the graphics on slot 3. Resolution: The graphics ROMs connect to the system board through a series of 74F253 ICs. These are dual 1 of 4 line selectors. Pin 21B on the bottom cartridge slot connector's data wasn't seen on the output (pin 9) of the 74F253 at position D1. Patched the trace to fix. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 17, 2008, 01:27:47 AM Model: MVS MV-6
Symptom: Stuck in Watchdog (a.k.a. Click of Death) 6 slot board would constantly reset... Logic probe on pin 18 of the CPU confirmed that the reset line kept bouncing. This was the watchdog circuit trying to kickstart the CPU into booting. Checked the data lines and enable lines on the work RAM - checked fine. Checked the enable lines on the backup RAM and discovered that the WE* line on one of the RAMs was missing its signal and the OE* line on both RAM chips was missing its signal. Repaired the bad traces to fix the bottom board. It appears that something corroded the plate-thrus on the board. Seems to be a common occurance on all models of the MVS boards. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 17, 2008, 01:28:00 AM Model: MVS MV-6
Symptom: Graphics corruption Found and repaird 4 gouged traces on the top board. Traces were damaged due to insufficient padding when item was shipped. The top cover was bent and the traces were gouged by it. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 17, 2008, 01:28:28 AM Board: MVS MV-4
Symptom: Crosshatch of death Crosshatch of death is where the board shows the self test crosshatch screen. It is not recognizing any cartridges inserted into the board. This is a common problem on the older, larger 4 slot board. The NiCD backup battery will leak and eat through traces that run under and next to it. Trace the lines with a multimeter from the connector next to the battery and run jumpers to patch any bad traces. That connector is what the system uses to access the program ROMs on the cartridges. If it can't read and run the program then it cannot detect and use the cartridges. ;) Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 17, 2008, 01:29:17 AM Model: MVS MV-4F (newer, smaller 4 slot)
Wow. This one was a bitch. Typical crosshatch problem, but the battery was not leaking and no traces were damaged near it. (Although the battery isn't in the same proximity to the traces on this board like on the older 4 slot board. Thus, this board doesn't suffer from the same Crosshatch of Death problem) I spent a lot of time troubleshooting and pinning out the SMT chips on the top board before moving down to the bottom board. The top board has the NEO-G0, NEO-244, and NEO-253 chips on it. It appears from the troubleshooting that the NEO-G0 chip is made up of 4 74LS245 chips. I haven't pinned out the 244 or the 253 chips but assume that they are similar (4 x 74LS244 and ? x 74LS253 chips) Enjoy the pinouts: Code: NEO-G0 chip at location D1 OK... After all of that I moved to the bottom board and checked the interface chips that connect the bottom board to the top board. WOW There were a lot of missing and incorrect signals coming from those chips. My logic probe got a workout on this system. Replaced the following bad chips to fix it: 74LS245 @ N1 74AS245 @ M4 74F245 @ N9 74F245 @ L9 74AS245 @ F11 74AS245 @ D11 74AS245 @ C11 I'm thinking that someone MUST have disconnected the two boards with the system powered up. That's the only thing I could think of that would've taken out all those chips at once. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 17, 2008, 01:29:58 AM Model: MVS MV-2
Symptom: Multiple - Video RAM Error $8000 and Calendar Error Had an MVS 2 slot sent to me for repair that had a couple of issues. The first was the typical Video SRAM issue at $8000 - The CXK5814 chips were both bad. The second issue was the game was stuck at the green screen. It would boot to the Backup RAM test if you turned all the DIPs on and would work fine with a UniBIOS chip. It was a Calendar Error problem. This problem does not always show up as the text "Calendar Error" on the screen. It may manifest itself as a "stuck on green screen" problem. Armed with my trusty logic probe the calendar IC (D4990) checked like this: Code: Pin 1 - H Hmmm... Crystal looks to be defective. Grabbed a working board and the signals look like this: Code: Pin 1 - H OK - Really looks like a bad crystal now. Swapped one off a parts board and POOF. System is now working. Hope the logic readings help you troubleshoot your system if you ever need it. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 17, 2008, 01:30:49 AM Model: MVS MV-4
Symptom: Stuck in Watchdog (Click of Death) Board gave garbage on the screen with constant clicking sound. In other words, it was dead and the watchdog circuit was resetting the CPU. Replaced a shorted 74AS245 at location B7. It was shorted internally and was getting red hot. Board powered up with a Video RAM error at 8000. Replaced the lower bank IC at L11 to finish repairing the board. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 17, 2008, 01:31:07 AM Model: MVS MV-2
Symptom: Will not boot. Resets. This one is a 2 slot that was shipped to me with the description of "stuck on green screen with garbage" When it arrived I hooked it up and it would get to the green screen as normal but would then reboot. This cycle repeated indefinitely. Battery had leaked and there was corrosion on some of the board traces. It was not a Calendar Error issue as it rebooted. Calendar error would've manifested itself by freezing on the green screen and not rebooting. Pin 20 of the backup RAM was missing its signal. Removed the battery, cleaned the board, replaced the corroded 74HC32 at location J2, and patched a corroded trace between J2 Pin 2 and transistor C1815 to fix. Replaced the battery with a new one and tested the board. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 17, 2008, 01:31:21 AM Model: MVS MV-4
Symptom: Garbage on screen / Click of Death (Stuck in Watchdog) This one had some physical damage that someone did a half-ass repair on. It's ugly as sin but the trace they patched is working. The board would display nothing but garbage and would constantly do a click click click - watchdog circuit was trying to restart the system. Replaced 2 74LS245 ICs at locations B7 and B8. Both were shorted and getting very hot. Board was still in watchdog restart. Patched a bad trace on data line D16 between the upper Backup RAM and the upper Data RAM. Now the board would constantly go through self test and restart with garbage on the screen. It was a different restart than with the watchdog circuit. Examined the board under a magnifying glass and found one more gouged trace the previous tech missed between data line D1 on the CPU and pin 60 on the PRO-C0 chip. Patched the trace and the board is now running fine. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 17, 2008, 01:31:41 AM Model: MVS MV-2
Symptom: Vertical bars through graphics This 2 slot had some bad battery damage and vertical bars through the Neo Geo logo and certain sprites. Checked the ROM Data Lines on the cart slot pins A19/B19 through A26/B26 with the logic probe. Cart was working fine. Followed the traces to the NEO-257 IC at J2 with the logic probe. Traces were good. Followed the outputs of the NEO-257 IC to the NEO-ZMC2 IC. Two of the data lines (D0 and D1) were missing from the NEO-257. Replaced the surface mount NEO-257 IC at J2 with one pulled from a parts board to fix. Cleaned the board & replaced the battery as well. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 17, 2008, 01:32:04 AM Model: MVS MV-2
Symptom: Random Backup RAM errors The control signals were missing from the Backup RAM chips. Installed a UniBIOS to further check the board and it would constantly crash. A close inspection of the board revealed corrosion damage from either liquid or rodents. Cleaned the board and found that the trace for address line A13 was damaged coming off of the CPU. Patched the trace and tested the board. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 17, 2008, 01:32:24 AM Troubleshooting with the UniBIOS chip
The UniBIOS chip can be used to bypass Backup RAM, Calendar Error, and other problems to allow for a board to be further tested. If the system bypasses errors and runs then odds are it will be an easier repair. If it's crashing then there are other problems that are masked by the error message. Check the BIOS socket, look for gouged traces, and check for corroded plated thru holes. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 17, 2008, 01:32:43 AM Model: MVS MV-2
Symptom: Backup RAM error Board was giving a Backup RAM error (written 5555 read 5500.) The "00" typically means the chip is missing control signals. Checked the board and it had 2 bad traces going to the control lines of the 2nd Backup RAM IC. Patched the traces and tested the board. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 17, 2008, 01:32:59 AM Model: MVS MV-4
Symptom: Corrupted Graphics The Neo Geo logo screen had the words broken into jumbled blocks and there were "0" (zeros) down the left and right sides of the screen. Checked the board for broken traces. Did not find any. Swapped the top board with my test board. Same problem - it's on the bottom board. Replaced the 2 74LS244 buffer chips that were driving the address lines for the graphics ROMs. No change. This was still an address line problem since the problems were in blocks and not in vertical lines on the screen. Took the logic probe and checked each address line at the top board. Noticed one of the lines only had a slow pulse on it instead of activity. Shorted it to the next address line over and the zeros went away and there was just garbled graphics. Traced that line back and found where there was a very small area of board between connector CN8 and the edge of the board that had taken a hit. Patched the broken trace to fix the board. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 17, 2008, 01:33:37 AM Here's a pinout for the custom NEO-ZMC2 chip
The NEO-ZMC2 IC is documented incorrectly on a few websites. It does NOT multiplex sound data. Instead it takes the foreground and background graphics (16 bits each for a total of 32 bits) and interfaces with a single 8 bit (8 traces) connection to the Neo graphics subsystem. On the older 2 slot the ZMC2 pins GAD0 through GAD3 and GBD0 through GBD3 connect to the NEO-C0 IC to get this multiplexed graphics data into the video subsystem. Standard conventions apply - Vcc = +5v, Gnd = ground, a "*" means active low (when there's a bar over top of the pin's function), etc... RJ Code: NEO-ZMC2 Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 17, 2008, 01:34:35 AM From Kyuusaku on the Neo-Geo.com forums:
Here's the ZMC2's early counterpart at least for home carts: ALPHA-8921 / PRO-CT0 Code: D1 odd.15 1 64 VCC Notes: test? = NC pins or pins with tracks that ONLY lead off the board for testing. A## are not address lines but home cart pin numbers as are B## Don't mind the bad formatting Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 17, 2008, 01:35:17 AM Here's the NEO-257 @ location J2 on the 2 slot board. (MV-2)
Code: Pin - function/chip connection/slot connection (cartridge pin function) Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 17, 2008, 01:36:18 AM If you look at a 74257 data sheet you will see that it is a 2 to 1 data multiplexer. The NEO-257 is simply 4 of these chips combined into one package to save some board space.
The hard part is that I cannot tell which pins are for "output enable" like on the 74257 since the only function that isn't set to ground or +5v is the one for input select. It appears these chips are set to always be enabled. Enjoy! Code: NEO-257 pinouts Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 17, 2008, 01:36:39 AM Troubleshooting Color and Sync problems on MVS boards:
This post is from the perspective of repairing a MVS 2F board - the newer version of the 2 slot - but will work for most other MVS boards. The output of the video subsection will go through the NEO-G0 chip then on to the Palette RAM (8k x 8bit SRAM) and the 74LS273 latches. From there it goes to a resistor ladder per color with a couple of the lines being buffered/amplified (higher current) by a 74LS05 IC before going out to the JAMMA connector. When troubleshooting MVS color issues take a moment to divide the problem into sections. 1. Palette, or Color RAM error 2. No Sync (either horizontal or vertical) 3. Missing or incorrect colors Part 1: Palette, or Color RAM error If there are Palette RAM problems this can be caused by a problem in any of the ICs connected to that data bus: NEO-G0 chip, Palette SRAM, or the 74LS273 latches. The easiest thing to do is to power OFF the board and check the data lines on the SRAM ICs for shorts to +5v or ground connections. If there are none then replace the SRAM first. If there is a short, remove the 74LS273 ICs first as they will be the most likely culprit. Check the data lines again. If the short is gone, replace the latches. If not, move on to the next chips, the SRAM. Repeat tests and replace the NEO-G0 last. Part 2: No Sync (either Horizontal or Vertical) The sync line goes from the NEO-I0 chip through a 100 ohm resistor to the JAMMA connector. It's also tied high to +5v through a 470 ohm resistor. Check both resistors. Replace if bad. If there is still no sync, replace the NEO-I0 chip. Part 3: Missing or incorrect colors Missing colors can be caused by any of the parts in the output section. Unless there's an esoteric problem with the Color RAM the digital part can be mostly taken out of the equation. The output is made up of the 74LS273 latches, a series of resistors forming a ladder network, and 74LS05 Hex Buffer/Inverter IC. With the power OFF, check the inputs and outputs of the 74LS05 IC for shorts to either +5v or ground connections. Replace the IC if any shorts are found. If there are shorts but the 74LS05 IC isn't it then replace the 74LS273 ICs. Next check the resistors for any that are burned. If the RGB outputs are shorted the most likely culprits will the the 220 ohm and 150 ohm resistors as these are the lower value resistors. (The lower the value the higher the current that will flow through during a short.) check these resistors with an ohmmeter and replace any that are not reading correctly. The next step is to check the outputs of the 74LS273 ICs with a logic probe. On the datasheet there are D and Q pins listed. The D is the input, the Q is the output. Check for signals on both sides. Replace the ICs that have inputs but no outputs between their D and Q pins. Hook everything back up after replacing the parts and give it a test! I had a board in the shop with missing red colors. There were no other symptoms on this board such as lines through images, etc... just screwy looking colors. I replaced the NEO-G0 IC before stepping back and taking a better look at the circuit. After analyzing the circuit I replaced a shorted 74LS05 IC and two bad resistors to fix the board. The 150 ohm and 220 ohm resistors were bad and the 74LS05 gate driving the 150 ohm resistor was shorted to ground. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 17, 2008, 01:37:49 AM Model: MVS MV-4
Dignosing bad RAM ICs Board is a NEO-MVH MV4 (4 slot) Code: Backup RAM Error: The Read code is broken up into 2 parts... AA and 2A The first 2 characters are the upper bits and are handled by the IC at D9 The second 2 characters are the lower bits and are handled by the IC at F9 --- Code: Video RAM Error: Same thing here... the Read code is broken up into 2 parts... 54 and 55 The first 2 characters are handled by the IC at L9 The second 2 characters are handled by the IC at K9 --- Work RAM is laid out backwards from Backup RAM and Video RAM on the NEO-MVH MV4 Code: Work RAM Error: (Yeah, I was too lazy to write down the exact address of the error...) The first 2 characters are the upper bits and are handled by the IC at H9 The second 2 characters are the lower bits and are handled by the IC at G9 Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 17, 2008, 01:38:37 AM Model: MVS MV-6
Diagnosing bad RAM ICs Here's the info on the 6 slot board: Upper Backup RAM: E9 Lower Backup RAM: F9 Upper Video RAM: L9 Lower Video RAM: K9 Upper Work RAM: J9 Lower Work RAM: H9 Just keep in mind that if you have an error at the bottom boundary then you need to check traces. For example a video error of: Code: Video RAM Error: Shows up on the zero boundary. You need to check to see if the traces (wiring that is on the circuit board) are all good. A bad trace or a bad chip can each cause this type of error. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 17, 2008, 01:39:29 AM Model: All MVS boards
Troubleshooting Backup RAM Errors If you see this for a Backup RAM Error: Code: Backup RAM Error: Then you have a different problem all together. This is caused by the chip not being selected properly for read/write access. This is almost always (well, I'd say > 99.5%) a problem with the chip or with the trace that is controlling the SRAM and NOT with the SRAM. Look for broken traces whether from battery leakage or someone scraping something across the board which physically damaged the traces. If that's not it then trace back the chip control traces to see what chip is feeding it. On the 32k x 8 SRAM ICs (the 62256 or equivalent) that are used for the Backup, Work, and Video RAM that would be: Code: Pin 27: *write (also known as *WE) - Write Enable OK, OK... the * in front means it is an active low signal. If it's high, it's not being signaled. If you get NO signal from your logic probe on one of the pins then you have an open trace for sure. Pin 20: should always be grounded on the Work RAM and Video RAM. That pin is directly connected to ground and if it isn't then you have a physically damaged trace. On the Backup RAM it is used to put the chips into low power standby mode. Pin 22 & 27 connect to different chips. These are the ones you are most concerned with when troubleshooting this type of problem. Follow the traces and repair corroded or otherwise damaged ones. (99.5% of the times this is the fix) Oh, when troubleshooting these you WILL have to strip off the red cardboard and the black foam under the circuit board in order to follow the traces. Have fun cleaning all that crap off. Yuck. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 17, 2008, 01:39:45 AM Board: MVS MV-2
Backup RAM locations When diagnosing the Backup RAM problems on a NEO-MVH MV-2 2-slot board: Upper Backup RAM location: H3 Lower Backup RAM location: H4 Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 17, 2008, 01:39:59 AM Model: MVS MV1FZS
Symptom: Crosshatch of Death This board does not suffer from the same battery damage induced Crosshatch of Death as the old style 4 slot board. The old-style 4 slot board's problem is one of legendary status and it should be documented that it is the ONLY board to consistently suffer from that kind of problem. Powered up the board and duplicated the symptoms. Looked for obvious signs of damage and found where the bottom of the board was gouged by something. Repaired 3 broken traces connecting to the cartridge slot resolve the crosshatch problem and repaired another 3 broken traces causing corrupt video. Always check the boards you are working on for signs of physical damage. It's pretty common on arcade boards. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 17, 2008, 01:40:17 AM Model: MVS MV-4F (newer style 4 slot)
Symptom: Z80 error and rapid audio click Had a MV4F board that came in with a Z80 error and a rapid clicking sound in the speakers. Strange thing is that as the speakers clicked the picture on the monitor flickered. (Little did I know this thing would kick my ass.) Replaced the Z80 CPU to fix the Z80 error. For some reason SNK put a Z80 in there and the board is labeled for a Z80A (higher speed) CPU. Now the system booted but flickered like mad. Audio ouptut was horribly distorted. With the audio down the system worked fine except the audio output IC was getting very hot. Recapped the audio section. No help. Replaced the audio output IC. No help. Replaced the volume control. No help. For some reason there was an oscillation happening in the audio circuit. This oscillation was causing the audio output IC to suck up large amounts of current. This was causing dropouts in the +12v output of my bench supply. These dropouts matched the screen flicker and the clicking of the speakers. Checked every trace in the audio section - all were good. Replaced the 3 op-amps. No help. Checked all the film caps (the non-electrolytic caps)... all checked good. All voltages looked OK but were a little lower than another MV4F board but they were within reason (+12v was a little low so the other voltages around the chip were correspondingly lower)... On a whim I removed both of the .1uf film caps on the speaker outputs. Audio was distorted but amplifier was stable. Next I put them back in circuit one at a time. The one on the right speaker was the cause of the problem. Replaced the cap and problem was still there. It looks like there's an issue with the ground trace inside the board. Removed the cap and ran the board for an hour at 3/4 volume with no problems. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 17, 2008, 01:40:37 AM Model: MVS MV-4F
Troubleshooting reset lines In working on a 4 slot board (MV4F) I encountered a Z80 error. The board had other issues (documented elsewhere) and when those were fixed and the board not yet reassembled, it gave a Z80 error. The reset line was held high. The reset line goes through the 74AS245 IC at location E11. It goes through the latch on pins 2 and 18. If that IC is bad the reset line could be stuck high or low, causing the Z80 CPU to never boot. That reset line must transistion from low to high to reset the Z80 CPU and make it start executing commands. In this case the problem came because the IC at E11 was pulled from the board as a step in troubleshooting. Once the IC was placed back in the board the reset line cycled normally and the Z80 booted. (This was also tested by jumpering the reset line on pin 15 of IC A9 to pin 26 of the Z80 before replacing the IC) Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 17, 2008, 01:40:55 AM Model: MVS MV-4F
Symptom: Stuck in Watchdog (Click of Death) Have a 4 slot board in to repair that was giving the click of death - stuck in watchdog - problem. This can be caused by many different problems, including: Bad CPU Bad Work SRAM Bad Backup SRAM Missing control signals on Work or Backup SRAM Shorted 74AS245 ICs buffering program ROMs on top board to CPU on bottom Short on address bus Short on data bus Missing address or data signals to chips First thing... Check for gouged traces. Found and fixed one. No effect. Next... Substitute BIOS. Nothing. Next... Check control signals on the Work RAM - Stuck high on pins 22 and 27. Next... Check control signals on the Backup RAM - Stuck high on pins 22 and 27. Next... Check control signals on the BIOS ROM - These were working. So we had a problem somewhere in the system to where it was trying to read the BIOS but not able to initialize hardware. Pulled the 74AS245 ICs buffering the data lines to the top board. Had no effect. Checked for more broken traces. No more were found. Checked the address and data lines going to the BIOS and SRAM ICs. All were good. Checked the data lines going to the NEO B1 chip. All were good. Checked the data lines. All were good. Next checked the A22* and A23* alternate lines. Missing one one! Ran a jumper wire from Pin 55 of the NEO-E0 IC to pin 117 of the NEO-B1 IC and the board came up! OOPS. Z80 Error. Reset line stuck high. On a Z80 since the reset line did not transition from low to high the Z80 never booted. Ran a jumper and the audio section worked. Replaced the pulled 74AS245 ICs and the board wouldnt' boot. Reset was stuck low. Turns out the reset line for the Z80 CPU and chips on the left side of the board goes through the 74AS245 IC at E11. Removed the jumper for the reset line and board booted normally. Plugged the top board back in, inserted some test carts and played a couple of games. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 17, 2008, 01:41:14 AM Model: MVS MV6
Symptom: Vertical lines in graphics Some background objects had vertical lines in them - in this case the "shock Troopers, 2nd Squad" floating logo had lines. It's the logo that is on the screen when it is playing in demo mode. I traced it to connector CN8 and started tracing it on the bottom board. UGH. It goes straight to NEO-CT0 As one final step before replacing that surface mount chip I checked the continuity between the top board and bottom. Bingo! No continuity. Next step - pull the boards apart and look at the connectors. They had something sticky on 2 of the pins and up in the socket. Desoldered and disassembled the socket then cleaned the pins on both connectors. Reassembled, resoldered into place, and tested. Board is fixed. Moral: Don't discount those board connections! Look at them closely to see if there is a foreign substance in there causing the problem. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 17, 2008, 01:41:31 AM Model: MVS MV4F
Symptom: Video RAM Error This board had multiple problems due to liquid damage. 4F board came in with a Video RAM error. Replaced the upper Video RAM IC and error went away but video was glitchy and had bad colors. Repaired a bad trace between the lower Video RAM IC and the LSPC2 IC. Glitching was gone but the colors were bad. Test screen showed blank for red, blue for both blue and green, and white was a little off color. Put in a UniBIOS chip and noticed the green was off and the low end of red was missing AND a white block was in the place of the lowest red color. (SNK BIOS shows 4 color boxes, one for each color. The UniBIOS chip shows color spectrum bands for each color) Checked the Color RAM and noticed that address line A2 was stuck low. Checked the NEO-B1 IC and noticed that A2 was stuck low there as well. Backtracked through the circuit and found that the TDI4 pin (pin 22 - signal name P16) was floating - no signal. Checked the other ends of the signal - the 74LS245 IC buffering the L0 ROM and pin 134 of the LSPC2 IC. They had signals. The trace under the LSPC2 connecting to pin 134 was bad. Ran a jumper wire between the 74LS245 and the NEO-B1 chip to fix. (It was WAY easier to solder to the big pin on the 245 than the small one on the LSPC2!) Audio was missing on one channel. Grabbed the oscilloscope and found that the volume control was bad. Replaced it with one off of a parts board. Reassembled the game and tested. Slot 3 had vertical lines on the screen through graphics. Patched a corroded trace to fix. Played a few games to test. Replaced the leaking battery then reassembled the board for one final test. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 17, 2008, 01:41:46 AM Model: MVS MV4F (newer smaller 4 slot)
Symptom: Missing/Garbled sound problem. This board has been a pain to track down. The board had been worked on before by another tech. Fixed a broken trace on pin 15 of IC 4N (74AS245 - other tech damage - grrrrr!) and the board would play sounds but was distorted on the higher frequency digital music. The sound ROMs are read through the YM2610 IC through data latches (74LS245) at board locations 2M and 2N. If the voice and lower frequency music notes are distorted then replace the IC at 2M. If the higher frequency music is distorted, replace the IC at 2N. On this board the replacement of 2N did not fix it. Board had a damaged trace internal to the board and the ground pin on IC 2N was not connected. Ran a patch to fix the board. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 17, 2008, 01:42:06 AM Fixed: AES
Symptom: Lines in overlay graphics (text, health, etc) and no sound Fixed a corroded trace leading to NEO-B1, pin 131, from the cartridge slot to restore the video. Looked at the YM3016 Sound DAC and there was no serial clock or data flowing from the YM2610 sound chip. Checked the Z80 CPU and it appeared good. Looked at the clock signal on the YM2610, pin 63, and it was dead. Traced it back to a 74AS04, pin 1 near location K4 and found a corroded plate thru hole on the trace. Patched the trace to finish the board repair. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 17, 2008, 01:42:23 AM Fixed: AES
Symptom: Garbage on screen Swapped out the Video RAM (62256 surface mount) chips and system would then give a yellow screen indicating a video RAM error. Checked the VRAM with a logic probe and saw that the address lines were pulsing regularly and were not pulsing erratic indicating they were being used when the system would run the Video RAM tests. Data lines, CE*, and W* lines appeared to be working normally. Checked the pins on the LSPC2 and found address line A1 was not pulsing with data. Traced it back to the BIOS chip and found the upper pad missing from the address line A1 pin. Ran a short jumper to fix the board. When someone replaced the BIOS on the console with the UniBIOS chip they socketed it, but not before pulling the upper pad and platethru removing the old chip. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 17, 2008, 01:42:38 AM Fixed: AES
Symptom: No video, would play blind Repaired bad trace on pin 126 of the NEO-B1 IC to fix the video clock and bring back the video. Fixed a bad trace on pin 125 of the NEO-B1 IC to fix a graphics corruption problem. Board played for about 10 minutes then rebooted to a red screen - bad Work RAM. Replaced the surface mount 62256 SRAM at R6 to bring it back from the dead. Finish the repair by running the game for a half hour to burn it in. From the last couple of repairs it appears that the AES suffers from the same random board corrosion problems that some of the MVS boards do. Some of the boards weren't cleaned very well at the factory and gunk left on them would eat random traces. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 17, 2008, 01:43:03 AM Resurrected: AES Parts Board
Symptoms: Dead, multiple cut traces, no video out. Had a complete parts board (no missing chips or damaged SMT chips) that was dead. Multiple solder bridges, traces cut, and missing the daughterboard. Installed a replacement daughterboard and patched 3 cut video (RGB) traces. Patched a broken trace connecting to pin 112 of the PRO-CT0 chip. Removed multiple solder bridges. Board would then try to boot but was stuck with garbage on the screen. Shorting out 2 data lines would result in a watchdog reset. No W* or CE* activity on the video RAM but did have activity on the work RAM and the system BIOS ROM. Board was trying to boot but never making through self test enough to put a color on the screen indicating what RAM was bad. Replaced the work RAM at R6 and the board would then boot to a blue screen with no cartridge plugged in indicating system's RAM was working properly. The video output was distorted and would fade in and out during the self test. Checked the CXA1145 RGB Encoder chip for broken traces as that chip looked to have been replaced before. Found a break between the pad and trace on Pin 13 (I REF connection.) Patched the trace to fix the video. Board would then boot and run but had connection problems with the cartridges. The slot connectors were very loose - basically worn out. Replaced both connectors (100 pins per connector!) with ones pulled off of a parts board to fix the slot problems. Unit had a Japanese BIOS. Swapped that out for a European BIOS and socketed it. Board played until it got hot then would randomly reboot. Board would also reboot when tapped or flexed. Used an eraser attached to a #2 pencil to just barely touch each pin on the NEO chipset chips and found the LSPC-A0 IC was the culprit. Resoldered the IC then was able to shake and tap the board without it rebooting. Let the board play for an hour to test. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 17, 2008, 01:43:20 AM Model: MVS MV-2F
Symptom: Audio would cut in & out Cleaned corrosion off of 2 ICs, installed an audio cap kit, and reset the backup RAM. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 17, 2008, 01:43:39 AM Model: MVS MV4
Symptom: Audio would cut in & out Installed an audio cap kit, and reset the backup RAM. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 17, 2008, 01:44:00 AM Model: MVS MV4
Symptom: Lines in background graphics and audio would cut in & out Swapped top board out and narrowed problem down to the bottom board. Found a gouged trace between pin 27A on connector CN9 and pin 8 of IC PRO-CT0. Patched trace to fix the graphics problem. Installed an audio cap kit and reset the backup RAM to finish the repair. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 17, 2008, 01:44:15 AM Model: MVS MV-4F
Symptom: Lines in background AND foreground graphics. No audio but board would make popping sounds and the screen would flicker with the pops. Board had strange graphics corruption on foreground and background graphics. This was different than what is normally seen as evenly spaced lines (1 bad line showing up out of every 8 bits across the screen) and instead was like every other line was missing. Swapped top board out and narrowed problem down to the bottom board. Checked the 74xx245 buffers between the top and bottom board. No problems found. Put the board under the magnifying lamp and found shorted pins from pin 65 to pin 80 (65 through 76 are ground pins anyway) on the NEO-ZMC2 IC at location 11M. Resoldered the pins to fix the graphics problem. Installed an audio cap kit and reset the backup RAM to finish the repair. It appeared to be leftover solder from when it was factory soldered that finally bridged the trace between pin 79 and 80. There were solder blobs between every pin down that side of the chip but only 79 and 80 appeared to be shorted. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 17, 2008, 01:44:35 AM Model: MVS MV-2F
Symptom: Graphics corruption and customer requested an audio cap kit to be installed. Screen looked like line 1 was missing every odd pixel and line 2 was missing every even pixel - repeat all the way down the screen. Some graphics elements were duplicated on the screen in the middle but were garbled and shrunken horizontally. Foreground and background graphics were affected but overlay text & health bars were not. The Neo Geo splash screen was affected but the "Winners don't do drugs" screen was normal. Board had horrible patch work done to fix some cut traces that was covered with hot glue. I removed and redid the patchwork. They missed 2 traces that needed patching and a couple of the pins were shorting together. I cut the bad part of the traces out so the gouged ends wouldn’t touch each other then resoldered in new wire patches. Resoldered the NEO-B1 and the LSPCA2 ICs to fix the graphics corruption problem and installed the audio cap kit. The 2 slot board didn’t have any support legs under the slot sockets. I suspect the flexing of the board by inserting and removing cartridges popped the legs loose from the solder pads on the board. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 17, 2008, 01:44:55 AM Model: MVS MV-2F
Symptom: Calendar error Chip tested good by substitution. Replaced crystal but oscillator would not come up. Chip was in error condition with an output that slowly cycled high-low repeatedly. Checked all inputs/outputs on the chip and they all appeared normal. Checked power to the chip with a multimeter even though the power connections showed logic "high" - the chip power was not at the proper 5.0 volt levels. Jumpered a corroded platethru to fix the board. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 17, 2008, 01:45:19 AM Model: MV-6 (6 slot)
Symptom: Bad Video RAM and graphics corruption Battery leaked and caused corrosion on the board and it had a Video RAM error at $8000 - Written 5555 Read 5FFF. Replaced and socketed both CXK5814 ICs to fix the Video RAM error. Removed the battery and cleaned up the corrosion some. The board would work but then had a funky video problem. This wasn't a normal vertical line through the images type of problem. It looked like horizontal lines through all images. It started with overlay graphics, moved to foreground moving objects and then on to backgrounds. It also got worse as the board heated up. Resoldered the NEO-B0, PRO-C0, and LSPC surface mount ICs. This helped some but not much. Running a finger across the board would cause the problem to get worse if you touched the area around the 74HC32 IC at C6. Replaced that IC but it had no effect. Broke out the component cooler and sprayed the PC board under each chip around the 74HC32 and found that the clock driver IC, a 74LS368 was bad. Spraying it with component cooler immediately fixed the graphics problems until the chip heated up again. Replaced the chip and played a game of Shock Troopers 2nd Squad. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 17, 2008, 01:45:32 AM Model: MVS MV2 (older 2 slot)
Symptom: Lines in foreground (player) AND background objects On the 2 slot Neo Geo boards the NEO-257 ICs are the 2 to 1 multiplexer ICs that choose which slot to get the graphics data from. There are 3 of them on the board. If one of these is bad then there will be lines in the graphics elements they are selecting. Top left is background graphics, bottom left is player graphics, and the one on the right side is for text and other overlaid objects. Replaced both of the left side NEO-257 ICs and the corruption was still there. Logic probe showed that the data was coming in and exiting the NEO-257 ICs correctly but I thought that maybe they were garbling the data. Nope. Problem still there. Did some further tracing down to where the data goes to the NEO-C0 chip. It flows from the 257s through the ZMC2 IC and then on to the C0 chip. Replaced the NEO-ZMC2 IC and tested the board. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 17, 2008, 01:45:51 AM Board: MVS MV4
Symptom: Click of Death Board was stuck in watchdog reset and had battery corrosion damage. Board already had wire jumpers already on it to fix a crosshatch of death problem. Cleaned the corrosion as best possible. Checked the control lines on the Backup RAM and Work RAM. They were stuck high meaning the chips weren't being accessed. Checked the enable line (pin 20) on the BIOS and it was stuck high. There was a problem in the decode or read/write circuitry. Checked around the chips near the battery for traces eaten by corrosion. Found pin 9 on the 74LS05 at location D11 had a bad trace connecting to pin 5 of the 74LS259 at location C5. Ran a jumper to fix the board. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 17, 2008, 01:46:22 AM Model: MVS MV4
Symptom: lines in graphics and sound problems on top board Swapped top boards out to narrow problem to the top board. Lines in the graphics were NOT the same for all 4 slots. Slot 4 was perfect. Slot 3 had 2 repeating vertical lines. Slot 2 had a single repeating vertical line. Slot 1 had every other vertical line missing. All slots had the same sound problems: missing tunes, incorrect tunes, and garbled sound effects. Found 3 bad traces in the sound circuitry between the board connector CN11 and the buffer/latch chips. Fixed at trace between pin 4 of R6, L6, G6, and C6 and pin 5A of CN11. Fixed a trace between 6B of CN11 and pin 3 of S6, M6, H6, and D6. Fixed a trace between 12B of CN11 and pin 9 of S6, M6, H6, and D6. Tested all 4 slots and sound was working fine. Checked slot 3 and found 2 bad traces in the area between the slot and the 4 to 1 data selector IC (74F253) at A7 and at B7. Ran a jumper from pin 4 of A7 to cartridge connector CTRG5, pin 33A and a jumper from pin 4 of B7 to CTRG5, pin 34A to fix the graphics problem on slot 3. Checked slot 2 and found a nasty looking signal on pin 11 of the 4 to 1 data selector IC at C1 (74F253). Checked continuity to pin 20B of CTRG3 and found it good. Looked closely at the pin on the cartridge slot and found slight corrosion. Cleaned the pin and the slot tested good. Slot 1 had a bad trace between pin 46 of CTRG1 and pin 10 of P7 (74F253). Jumpered the trace and tested the slot. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 17, 2008, 01:46:43 AM Model: MV2
Symptom: Backup RAM Error Board would get to the green screen then reboot. This was a constant repeating cycle. Flipped all the dip switches to run the system through a Backup RAM test. It gave a Backup RAM error with the message Written: 5555 Read: B240 (The B240 error is stuff of legend over on the Neo-Geo.com forums.) Checked the Backup RAM with a logic probe and found pin 20 (CS*) was dead on both. Traced it back to the 74HC32 and back to the battery backup circuit. Traces were good. The resistors and diodes in that section were good. Checked the C1815 transistor with an ohmmeter and it was OPEN from collector to emitter. Replaced the transistor and the board booted right up. I have to say this is the first time I've seen an open transistor that wasn't blown in pieces. I think the corrosion from the battery must've traveled up the legs and into the body of the transistor and caused it. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 17, 2008, 01:46:54 AM Model: MV2F
Symptom: Missing audio from right channel after 5 minutes This board was traded in as a "dead" board purchased off of eBay towards the repair of another board. Found 1 penny in the bottom of the box and found another two pennies and a dime wedged in the memory card slot. Removed the coins, straightened the pins and tested the board. Fixed the audio problem by recapping the audio section. Replaced the memory card connector with one from a parts board to finish the repair. The original 2 slot arcade cabinet is set up to where the player can insert a memory card to save games. Apparently someone shoved coins in this slot. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 17, 2008, 01:47:19 AM Model MV4FT2 (The 3rd, newest, and smallest verison of the 4 slot)
Symptom: Carts would not work in slots 1 and 2. No audio. Strange thing was that you could put carts in 3 or 4... or 3 and 4 and it would work. Put a cart in slot 2 or slot 1 and you would get a crosshatch. Put a cart in 2, 3, and 4 then all three slots were usable. Put carts in all slots and the board would constantly reboot after doing self tests. Repaired a bad trace between Slot 1 and 2, pin 13B on the program board connector and IC 1A, a NEO-244, pin 38. This was the program data line D8. Now all four slots would run cartridges. The audio problem was tough to track down. The audio test worked so the bottom board was at least generating audio from the diagnostics. Swapped the NEO-244 IC at A2. Nothing. Traced down all the connections between the slots and the NEO chips and then the NEO chips to the CN9 connector. Then traced it from the CN9 connector on the bottom board back through the 74xx logic to the 2610 Yamaha chip. Everything tested good. Frustrated, I cleared the backup RAM and the sound magically returned. AAAAAAAAAAAAAHHHHHH!!!!! Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 17, 2008, 01:47:35 AM Model: MV1
Symptom: Backup RAM Error Board was giving Backup RAM Error: Written 5555 Read 7255 Battery leaked on the board. Checked the traces to the Backup RAM. They tested good. Removed the battery, cleaned the corrosion, patched 2 bad traces from the NEO-F0 IC to the DIP switches, and replaced the Backup RAM at H6. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 17, 2008, 01:47:50 AM Model: MV1
Troubleshooting RAM Problems When troubleshooting RAM Problems on the MV1 the error message (Read 7255) can be broken down into upper bits (72) and lower bits (55) The bits are kept in RAM as follows: Backup RAM: Upper H6, Lower H5 Work RAM: Upper G3, Lower G4 The rest of the ICs will get filled in as I troubleshoot other boards. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on November 10, 2008, 11:00:21 PM Model: MV1C
Symptom: No video sync Board had no video sync. There is a 470 ohm SMT resistor tying the sync line high then a 100 ohm SMT resistor inline with a 74HC32 surface mount IC. The IC had inputs but the output was stuck high. Replaced the IC and the 100 ohm surface mount resistor. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on November 20, 2008, 02:00:20 AM Model: MVS - MV2F
Symptom: Lines in player graphics and some background graphics for slot 2. Logic probe showed pin 20 on the ZMC2 chip stuck high when a cart was being accessed in slot 2. Checked pin 9 on the NEO-257 at H/J2 and it was stuck high. Checked pin 16 and it had garbage for the inputs. Checked the trace from the NEO-257 to the slot and it was good. Replaced the NEO-257 IC to fix the board as its inputs were damaged. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on November 30, 2008, 01:59:44 AM Model: Bootleg MV1C
Symptom: Plays for a couple of minutes then starts glitching Board would get horizontal streaks on the display. Would get worse as game was played. Pushing on the SMT chips had no effect. Power cycled game and it worked again but played slower and the sounds were played slower as well then started streaking more and more until it lost sync and died. Resoldered the main video IC and system clock driver IC to no effect. No clock signal was coming from the 24MHz crystal. Checked the 1M and 100 ohm resistors and the 2 caps connected to the crystal. Checked soldering on the system clock driver IC. All checked good. Replaced the crystal and played a few games. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on November 30, 2008, 02:52:21 AM Model: Bootleg MV1C
Symptom: Missing BIOS. Burned a replacement BIOS ROM. Board booted and played but had no sound. Replaced missing sound pot and fixed a bad trace. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on November 30, 2008, 02:53:41 AM Model: MV-1F
Symptom: Requires separate coin mechs for player 1 and player 2. Unit had a 2 slot BIOS in it. (usa_2slt.bin) Replaced it with the standard USA BIOS (neo-geo.rom image) and played a couple of games to test. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on November 30, 2008, 05:43:33 AM Model: MV4FS
Symptom: Dead. Had a note taped to it that there were lines in the graphics. Unit was missing the BIOS chip. Programmed a replacement chip (27C1024) and booted it. It had lines in the graphics and was missing sounds. Board had been repaired before and had many chips replaced on upper and lower boards. It also had a dark liquid spill on the top board. Checked all the previous trace repairs. Reset the Backup RAM to fix the sound issue. Cleaned the top board and the slot connectors to fix the lines in the graphics. Reassembled the board and replaced all the missing standoffs, screws, and mounting feet. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on December 11, 2008, 03:58:14 AM Model: MV4
Symptom: Dead. Click of death. Bottom board had severe corrosion damage on the platethru holes and was beyond economical repair. Contacted customer and swapped out the bottom board with one that was already repaired. Slot 1, 2, and 3 had lines through the graphics and if a cart in slot 1 was bumped the board would reset. Cleaned the top boad and slots thoroughly to fix slots 2/3. Replaced the slot 1 connectors with ones pulled from a parts board to finish the repair. (No new ones are available.) Customer reported the boardset was 300 feet from the ocean at an arcade which would explain the corrosion damage. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on January 08, 2009, 03:26:31 AM Model: MVS MV-4
Symptom: Multiple - Backup RAM Error $D000, Calendar Error, audio, and slot problems Purchased a 4 slot board to refurb and resell. It was sold as having a "RAM Error" The board had a Backup RAM Error at $D000, Written 5555, Read 55F8. Since it was at the zero address boundary I checked the enable lines and the R/W line first. The R/W line was dead on the lower Backup RAM chip. Soldered in a 30ga kynar jumper between pin 8 of the 74HC32 IC at D8 and pin 27 of the Backup RAM at locaiton K8. The board now booted but was stuck at the green screen - a calendar chip problem. The logic probe showed normal signals on all the pins of the 4990 IC but gave strange readings on the crystal. Checked the crystal with an oscilloscope. It was dead. Checked the traces around the crystal and found the trace from pin 13 on the 4990 IC was bad. Soldered in a kynar jumper and the board booted to the crosshatch. Ran the board through tests and found the left audio channel was dead. Installed a cap kit to fix the audio problems. Board would boot but not recognize cartridges. Isolated this to the top board. Checked the board thoroughly and found that the slots were dirty. Cleaned the board and slots then ran the board through a final set of tests in preparation for resale. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on January 08, 2009, 03:33:22 AM Model: MV-4
Symptom: Crosshatch of death (wouldn't recognize cartridges) Checked the traces under the battery and found the 3rd trace bad. Jumpered the first 4 traces as they were discolored and would eventually go bad. Installed a new battery and tested the system. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on January 10, 2009, 02:36:27 AM Model: MV1
Symtpom: Audio cuts out The audio would get very low and sputtery sounding at intermittent times. Board had a cap kit already installed. Narrowed it down to a dirty Stereo/Mono selector switch. Cleaned the Stereo/Mono selector switch and tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on January 11, 2009, 02:54:00 AM Model: MV4
Symptom: Video RAM error Board gave a Video RAM Error. Address 00000E17, Write 5555, Read 5557 Replaced the surface mount video RAM IC at K9. Reset the Clock/Calendar, replaced 2 missing screws, and tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on January 11, 2009, 04:09:24 AM Model: MV4
Symptom: Z80 Error Replaced the Z80 chip with a Z80A. Game would then boot but had no audio. Installed an audio cap kit to finish the repair. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on January 14, 2009, 04:41:16 AM Model: AES
Tip: Diagnosing RAM problems The AES is different than the MVS in that it does not display error messages on the screen if there are hardware problems. To diagnose problems, boot the system without a cartridge installed. The screen will turn different colors depending on the errors. Blue = All tests passed Red = WorkRAM error ($100000 region) Green = PaletteRAM error ($400000 region) Yellow = VideoRAM error Pink = Bios selfcheck error ($C00000 region) Cyan = Memory card error The AES tests will only test the memory card if it is inserted and it is blank. It does NOT test the Z80 or other parts of the sound subsystem. Many thanks to the folks at the neo-geo.com forums for this list! Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on January 24, 2009, 06:02:55 AM Model: MVS-2F
Symptom: Calendar Error message and Battery acid damage Removed Battery and cleaned the acid damage. Repaired 1 broken trace to fix the calendar problem. Board would boot and run but had no audio and lines on slot 2 that would come and go if the cartridge was wiggled. Cleaned slots and whole board thoroughly then installed an audio cap kit and a new battery. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on January 30, 2009, 04:41:10 AM Model: MV1C
Symptom: Dead MV1C arrived missing fuse. Replaced fuse and board was dead. Would come up with a white screen with 4 colored blocks. Cleaned board and inspected for damage. Resistor R79 (100 ohms) was broken off the bottom of the board. Replaced it with one from a parts board. Still dead. Inspected the board further and found pin 40 (Vcc) was broken off of the BIOS ROM. Jumpered the pin to the body with a multimeter probe and the board booted to Work RAM test. Replaced the BIOS ROM with one from a parts board and set all jumpers to off. Board would boot but get stuck on a green screen. Checked the clock/calendar crystal. It was dead. Replaced it and played a few games to test the board. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on January 31, 2009, 05:01:14 AM Model: AES
Symptom: Needed custom BIOS installed Customer wanted the system upgraded. It had the old Debug BIOS stacked on top of the AES BIOS chip. Removed 1 resistor and the double stacked chips. Installed a new socket and a freshly programmed UniBIOS chip. Board would not boot. The UniBIOS file supplied by the customer was corrupt. Programmed another EPROM with the UniBIOS 2.3 code and tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on January 31, 2009, 05:01:54 AM Model: MV1C
Symptom: Backup RAM Errors Backup RAM Error: Written: 5555 Read 5540 Found a broken trace between RAM 2 and RAM 4 on pin 20. Jumpered pin 20 from RAM 2 to pin 10 on U3 (74HC32.) Board then booted to: Backup RAM Error: Written: 5555 Read 558E Found an erratic signal on the R/W line (pin 27) of RAM 2. Jumpered pin 27 from RAM 2 to pin 6 on U3 (74HC32.) Cleaned the board and played a few games. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on February 01, 2009, 09:45:42 PM Model: MV4FT2
Symptom: Click of Death Board was stuck with a click of death problem. Swapped BIOS chips, still dead. Checked the address and data lines. All 16 data lines were stuck high. Used the "well calibrated finger" and found that the IC at location N3 (74AS245) connecting the CPU to the sound subsystem was shorted internally and getting very hot. Pulled the IC and tested it. It was bad, but replacing it did not free up the data lines. Pulled the 2 74AS245 latches at C11 and D11 connecting the CPU data lines to the cartridge program ROM data lines. When tested they were found to be bad. Replaced them and system then booted up to a Video RAM error at 8000, written 5555 read 0000. Replaced both SRAM ICs to finish up the repair and tested the board. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on February 02, 2009, 02:05:33 AM Model: MV2F
Symptom: Locks up at boot When running a cartridge with the "Winners Don't Do Drugs" screen, it would show the Neo Geo splash screen then the Winners screen before locking up. Installed a UniBIOS chip and retrieved the crash info. The developer of the UniBIOS chip said the game was crashing within code. Ran extended Work RAM tests (turn on all DIP switches) but found no errors. Ran CRC tests on the cartridges and found that none of the carts gave good CRC checks in this board. Used a logic probe and verified that all of the program ROM data lines and address lines were active. Found that address line A18 was dead. The trace was good between slot 1 and slot 2 but not between the slots and the NEO-E0 chip, pin 40, and board location G3. Ran a jumper to fix the board. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on February 04, 2009, 12:43:57 AM Model: MV4
Symptom: Audio cuts in & out, memory backup not working Board had been worked on before for an audio problem and had incorrect caps installed. Installed a cap kit and jumpered a damaged trace. Replaced the backup battery then installed 2 missing hex standoffs and mounting feet. Replaced 2 broken mounting feet. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on February 04, 2009, 01:52:38 AM Model: MV4
Symtpom: Audio cuts in & out Installed an audio cap kit and tested the board. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on February 09, 2009, 01:33:56 AM Model: MV4
Symptom: Dead - no click of death Board fired up to a blank screen. No garbage on screen and no click of death. Power cycled the board a couple of times and it came up with a Work RAM error but no diagnostic info such as at what address or what was written/read. Replaced the work SRAM IC at location D9 and tested board. No audio. Installed an audio cap kit to finish the repair and tested the board. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on February 10, 2009, 04:37:12 AM Model: AES
Symptom: No sound This was a bear to track down. Cleaned corrosion off the board. Cleaned the right end pins on each slot and socketed 3 chips to check the traces under them. Found a bad trace between E9 pin 6 (74LS11) and CN4 (front slot) pin 47A and Q3 pin 9 (74LS04). This trace was the Chip Enable pin on the sound program ROM. Patched the trace and tested the board. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on February 21, 2009, 12:55:25 AM Model: Ikari III - The Rescue
Symptom: Garbled graphics a lines on the screen Checked the board for damaged traces then started checking the video SRAM with the well calibrated finger. Found one (and received a blister on the finger) that was internally shorted. Found another one hotter than the others and checked it with a logic probe. It had bad looking signals on the data lines. Replaced both SRAM ICs and tested the game. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on February 26, 2009, 01:34:46 AM Model: MV1
Symptom: Z80 Error Swapped the Z80 chip with the proper Z80A. No change. Inspected the board closely and found some corrosion on 4 pins of a surface mount IC connected to the Z80 CPU. Continuity tests showed one trace was open. Cleaned the board and soldered in Kynar jumpers pm all 4 corroded traces to repair it. Only one was needed to do the repair but by doing all 4 the board will last a lot longer for the customer. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on March 08, 2009, 03:00:57 AM Model: MV2F
Symptom: Vertical lines in backgrounds Pin 16 (D3 for Slot 2) on the NE0-257 IC at J2 was shorted to ground. Removed the IC and checked the trace on the board. The short was gone and was internal to the chip. Replaced the chip and tested the board. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on March 17, 2009, 10:52:56 PM Model: MV4
Symptom: Slot 1 dead. Missing left channel on audio. Checked the address lines and data lines on the Program ROMs for slot one. Found pin 15A on CTRG2 connector for slot 1 had a bad trace between it and C3 pin 7 (74LS245 IC). Patched the trace and tested the board. Installed an audio cap kit to finish the repair. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on March 19, 2009, 04:29:10 AM Tip: Cartridge ROMs
When troubleshooting cartridge issues it helps to know which ROM does what. P ROM - 68K program (16-bit) V1 ROM - ADPCM-A port (8-bit) <-- Music & sound samples V2 ROM - ADPCM-B port (8-bit) <-- Music & sound samples C ROM - VDP object tiles (32-bit) S ROM - VDP overlay tiles (8-bit) M ROM - Z80 program (8-bit) <-- Sound Program ROM Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on March 19, 2009, 04:34:51 AM Model: MV4
Symptom: No audio from any slot or from self test Installed an audio cap kit and the board would play the self test sounds but had no audio from carts. Replaced 1 74245 IC at location R1 on the lower board. The board would then play music and partial sound from carts. The Z80 CPU would lock up at set places on game cartridges when certain sounds were to be played. Isolated the problem to the top board. Checked the ADPCM ROM address/data/control lines. They were perfect. Checked the sound program ROM. Pin 3 was stuck low. Replaced a shorted 74LS244 at location N5 on the top board to finish the repair. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on March 20, 2009, 01:42:45 AM Model: MV4
Symptom: Z80 ERROR Replaced the Z80 with the proper Z80A chip for the board. SNK was cheap and used slower rated parts at overclocked speeds. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on March 30, 2009, 02:14:36 AM Model: MV4
Symptom Backup RAM Error Backup RAM Error: Address D0814 Written 5555 Read 55D5. Replaced bad Backup RAM chip at D9. Board then came up with a Video RAM Error: Address 00803 Written AAAA Read ADAA. Replaced the Video SRAM IC at location L9. Board came up but had very faint audio output. Installed an audio cap kit to finish the repair. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on March 30, 2009, 10:26:55 PM Model: MV4
Symptom: "Z80 Error and sound failing" Could not duplicate a Z80 error. The board immediately powered up with a Work RAM Error: Address: 00100008 Written AAAA Read AAA2. Replaced a bad surface mount RAM at G9. Tested audio levels in the hardware test menu. Right channel was barely audible and left was not audible at all. Installed cap kit and tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on April 11, 2009, 04:15:40 AM Model: MV1FS
Symptom: Stuck on Green - Calendar Error Board had damage from a leaking battery. Customer removed battery before sending the board in. Cleaned the board and jumpered a bad trace to fix the calendar problem. Board was stuck in a reboot cycle. Repaired another dead trace in the battery section that was sending power to a 74HC32 as part of the circuit for the enable lines on the Backup RAM. Replaced the missing battery and tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on April 22, 2009, 12:46:45 AM Model: MV4
Symptom: Stuck on Crosshatch User attempted repair damage. Tried a battery swap and board would no longer recognize any cartridge installed. Found a knife scrape on the bottom board. Repaired 1 bad trace and jumpered another bad trace. Replaced 2 stripped screws. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on May 06, 2009, 01:59:15 AM Model: MV2F
Symptom: Z80 Error Replaced a bad Z80 chip with the proper (and faster rated) Z80A. Tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on May 13, 2009, 03:00:53 AM Model: MV4FT2
Symptom: Audio would cut in & out. The interconnect between the top and bottom boards that carries the signals to/from the Audio ROMs was broken on the bottom board side. Replaced the connector, installed a cap kit and a new battery, then tested the game. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on May 13, 2009, 03:01:23 AM Model: MV4
Symptom: No audio. Would not keep settings in memory. Battery read 7mv instead of 3.6v. Ran the game for an hour and the battery took no charge. Installed an audio cap kit and a new battery. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on June 02, 2009, 02:17:56 AM Model: Street Smart
Symtpom: Dead Replaced missing 6264 SRAM IC, fixed a short on the ROM board connector CN1 and resoldered it. Set the DIP switches and tested game. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on June 05, 2009, 10:59:57 PM Model: Street Smart
Symtpom: Dead Fixed bent pins on the audio output IC. The 12v line was shorted to ground and causing the switching power supply to go into shutdown. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on June 12, 2009, 03:40:11 AM Model: Neo Geo AES
Symptom: Red screen with no cartridge installed This symptom is indicative of bad Work RAM. Checked the board and found that several of the memory lines on both Work SRAM chips had been partially desoldered and that there was some chemical corrosion on the pads. There was also one existing repaired trace and several data line traces that had their coating scraped badly. Cleaned the pads up, resoldered the data lines, and checked continuity to the CPU. Patched one bad data line and coated the bare traces to protect them. Tested the game. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on June 26, 2009, 03:53:55 AM Model: MV4
Symptom: Click of death Battery leaked on the board and ate many traces. Cleaned both the top and bottom boards. Attempted repair on the bottom board but it was uneconomical to repair. Swapped out the bottom board for one that was already repaired. Game then worked but Slot 4 had corrupt graphics. Repaired two traces on the top board to finish the repair. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on July 15, 2009, 01:38:38 AM Model: MV4
Symptom: Low audio and garbled sounds Installed an audio cap kit to restore sound and noticed that the sound effects and music were all mixed up. Generally this problem is caused by a bad IC at F1, F2, G1, or G2. Replaced those to no effect. Swapped out the SRAM and Z80 IC to no effect. After the board sat overnight it would play the audio test tones in the hardware tests as garbled sounds when cold. This is a problem with the digital sound circuit and not a problem with the bottom board interfacing with the top board. Replaced a bad YM2610 IC and tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on July 25, 2009, 04:58:39 AM Model: MV4
Symptom: Low audio and missing sounds Installed an audio cap kit to restore sound and noticed that the sound effects for spelling the bonus word in Shock Troopers, 2nd Squad was missing. In Metal Slug the bonus sound from picking up fruit or other non-gun objects was missing. Replaced a bad YM2610 IC and tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on August 13, 2009, 12:50:41 PM Tip: Neo-Geo Cartridge ROM Functions:
P: Program ROMs P1 is typically the main program ROM, it can be up to 8M and contains the entire game logic. Some old PROG boards use 2/4M ROMs so P2-4 can be the rest of the P1 address space. Then there's another address range used for a few different things such as the link circuitry, Fatal Fury 2 protection and later on it became used for another 8M+ of program ROM. ROMs mapped here are SP2 (P2 on the chip) if P1 is 8M. EP1 replaces P1 with updated program code. EP2 can be either the second half of EP1 if they're both 4M or can be the same thing as SP2 (8M+). V are YM2610 ADPCM data ROMs. There are actually two types of V ROM, one for the low frequency channel, one for the high. Games quickly started containing a chip called NEO-PCM which allows both channels to use the same ROM. C ROMs only contain sprite data (which also makes up the backgrounds on the Neo), not the fixed tile layer data. M ROM contains the Z80 sound engine program as well as the actual "track" sequences. Remember all sample data however is contained in the V ROMs. S aka the "FIX" layer ROM contains the fixed (non-scrollable) tilemap layer that overlays sprites. Life/POW bars are made of this. Thanks to Calpis on the Assemblergames.com forum for this info! Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on August 18, 2009, 01:31:07 AM Model: MV4
Symptom: RAM Error, written AAAA read A8AA Board was shipped in a box that didn't allow for sufficient packing. 2 standoffs and the top cover were bent. Replaced 1 bad SRAM IC at location H9, installed an audio cap kit, replaced 2 bent standoffs, and fixed the bent top cover. The audio is now loud and crisp. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on August 20, 2009, 02:34:22 AM Model: MV4
Symptom: Stuck in watchdog. Customer requested a UniBIOS upgrade and a new battery be installed. Repaired 3 broken traces. Tested board and found the audio level was low. Recapped the board to fix the audio problem. Replaced the battery and upgraded the system with a UniBIOS 3.0 chip. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on August 27, 2009, 04:05:59 AM Model: MV4
Symptom: Backup RAM Error Replaced bad surface mount SRAM IC and tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on August 30, 2009, 03:49:29 AM Model: MV4
Symptom: Backup RAM Error (Written 5555, Read D555) Replaced bad Backup RAM chip and tested board. Other Backup RAM chip was bad too. Replaced other Backup RAM chip and tested. No audio. Installed an audio cap kit and tested board. Replaced 3 missing screws holding the top cover on and inspected the top board for damage. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 06, 2009, 11:30:36 PM Model: MV1
Symptom: Sound dies after board is powered on for about 30 seconds Cleaned the Stereo/Mono audio selector switch and tested board. Customer requested an audio cap kit be installed. Installed the audio cap kit and tested board. Battery had started leaking. Contacted customer and replaced it per his request. Reset the Backup RAM and set the system date/time. Played a couple of games to test. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 07, 2009, 11:41:36 PM Model: MV1
Symptom: No Audio The Stereo/Mono switch was physically broken off the board. Jumpered the switch to put the board into stereo mode then recapped the audio section. Replace the leaking memory backup battery. Reset the Backup RAM, set the date/time, and tested the board. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 17, 2009, 02:15:11 AM Model: MV1
Symptom: Stuck on green Checked pin 14 for +5v when board was powered up. It was there. Checked the 32.768KHz clock crystal and found it was dead. Replaced the crystal and played a game to test the board. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 20, 2009, 01:11:13 AM Model: MV1FS
Symptom: Garbled audio The audio wasn't muffled but rather was garbled in the digital section of the board. Soldered over several scratched traces to protect them and checked the DAC and looping Op-Amp IC connected to the DAC. Found the battery had leaked. Cleaned the board, resoldered 2 corroded plate thru to trace connections to fix the audio, and replaced the battery. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on October 11, 2009, 07:23:32 PM Model: MV2F
Symptom: COLOR RAM ERROR Written 5555 Read 5755 Board came in with severe attempted repair damage. Removed both Color RAMs (4364/6264) and checked for damaged traces. Repaired 7 damaged traces and socketed the 2 Color RAMs. The Color RAMs tested good. Data 1 line on the Color RAM furthest away from the JAMMA connector had runaway pulses on pin 12. Removed the 74LS273 at location A8 and this did not affect the error message. Replaced the NEO-G0 custom IC at location B9 to repair the board. Testing the board revealed that P1 Up did not work. Repaired a corroded trace at the JAMMA connector to finish the board repair and tested. The memory backup battery had started leaking. Contacted the customer concerning the leaking battery and replaced it per his request. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on October 11, 2009, 07:31:58 PM Model: MV2F
Tip: Troubleshooting Color RAM Errors When troubleshooting Color RAM Error messages it's important to take the proper steps to quickly isolate the problems. If the error message isn't at the beginning of the bank then one of the SRAM chips is bad. The first 2 characters of the READ string is handled by one chip and the last 2 characters by the other. In other words: Written 5555 Read 5755 means the chip furthest from the JAMMA connector is bad. Written 5555 Read 5557 means the one closest to the JAMMA connector is bad. Replace the chip and test. If the error is at the beginning edge of the bank, follow the steps above and replace the appropriate Color RAM chip. If that does NOT fix the problem then more in depth troubleshooting is needed. First step is to check for damaged traces and repair them as necessary. Next, carefully examine the output resistor ladders for damaged resistors. If these are found, the problem will most likely be a bad or damaged 74LS273 IC causing the Color RAM Error messages. If the resistor ladder components are OK then check signals on the Color RAM with a logic probe. If signals are stuck low or high, check for shorts to ground. If the lines are not shorted then remove and test the Color RAM chips and 74LS273 ICs. If the lines are still stuck low then the problem will be with the NEO-G0 IC as it's the only component left to check. If the signals are racing on the affected data pin when checked with the logic probe then do the same thing: Remove and test the Color RAM chips and the 74LS273 IC connected to the racing data line. If the line is still racing with those removed then replace the NEO-G0 chip. Enjoy! Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on October 11, 2009, 07:48:30 PM Model: All
Tip: Checking the NiCd Battery for leakage One funny thing about NiCd batteries are that they leak after they go bad. This isn't a normal kind of leakage you would expect from a battery but is rather a crystalline growth that appears on the terminals and spreads across the board and follows traces. This will eventually turn a telltale blue but when first starting out looks like simple dust. Do not let this dust fool you! When the battery starts to leak it must be replaced ASAP as the leakage will only get worse. This will eat traces and component leads. It will ruin sockets, chips, resistors, capacitors, and more. It doesn't care if the board is a common cheapie or a rare expensive one. It will leak just the same. Here are 2 pics of the same battery. One is the shot of the positive terminal and the other of the negative. In one picture the solder joint is nice and shiny - a good looking solder joint. In the other you can see the growth on the battery and how it has already affected the solder joint. That isn't a cold solder joint but rather one that has been chemically corroded by the leakage from the battery. When replacing these old NiCd batteries it is OK to use NiMH types with the same form factor. It is also OK to replace them with a battery having a higher milliamp hour rating such as replacing a 50maH with a 70maH rated battery. Good luck, and replace those batteries before they ruin the game! Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on October 22, 2009, 12:47:13 AM Model: MV4
Symptom: Corrupt Graphics Repaired 7 broken traces and tested. The board had poor audio and a leaking battery. Replaced the battery and recapped the board to finish the repair. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on October 22, 2009, 12:48:54 AM Model: MV4
Symptom: RAM ERROR at location $8000 Replaced 2 bad CXK5814 SRAM Ics and tested board. Audio levels were low and the battery was leaking. Replaced the battery, recapped the audio section, and tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on December 21, 2009, 04:23:26 AM Model: MV1C
Symptom: Video RAM Error Replaced 2 62256 surface mount SRAM chips and tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on December 21, 2009, 04:23:51 AM Model: MV6
Symptom: Missing Audio on slots 4 through 6 Jumpered a bad trace between pin 1 on IC B13 and pin of B17. Tested Game. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on December 31, 2009, 02:44:23 AM Model: MV6
Symptom: Slots 4 and 5 dead Slots 4 and 5 would show crosshatch when a known good cartridge was installed. Cleaned the slots aggressively with very fine emery cloth as the slots had bad corrosion problems due to liquid (possibly rodent) damage. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on December 31, 2009, 02:44:32 AM Model: MV6
Symptom: Missing video on odd numbered slots Games would play fine in the even numbered slots. The odd numbered slots had audio, but missing video - foreground, background, and text were all missing. Repaired bad trace between D3 pin 11 and C29 pin 15. Tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on January 01, 2010, 06:22:22 AM Model: MV1FT
Symptom: Dead. Garbage on screen Straightened a bent pin on the BIOS ROM, powered up the game, and received a SYSTEM ROM ERROR message. Programmed a new BIOS ROM, booted the system, and received a Z80 ERROR message. Replaced the Z80 CPU and tested. Splash screen sound was normal, but the games sounds were horribly mangled. Repaired a damaged trace to finish the repair and tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on January 16, 2010, 05:10:43 AM Model: MV4
Symptom: Z80 ERROR Address line A16 on the sound subsystem was racing. Replaced the most common problem chips first: CPU, SRAM, and the 74LS244, but the problem remained. Replaced the SM1 ROM IC to fix the error. Installed a cap kit to fix low audio issues and cleaned the slots to fix cartridge issues. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on January 21, 2010, 01:47:10 PM Model: All MVS
Tip: BIOS Identification Here's a tip from a former SNK employee: Power up the MVS board without a cartridge installed. Look at the border color around the edge of the crosshatch screen. The color will reflect the region the BIOS is for. Green: 6 slot, an older BIOS Light Blue: USA BIOS, labeled SPU2 Dark Blue: Spanish BIOS, labeled SPS2 Red: Japanese BIOS, labeled SPJ2 Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on January 24, 2010, 05:22:35 AM Model: MV2
Symptom: Calendar Error Inspection of the board turned up gouged traces in several different spots. Removed 2 shorts and patched 9 broken traces. Tested game. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on February 03, 2010, 03:34:42 AM Model: Aero Fighters 3 - MVS cartridge
Symptom: Dead Board was a converted cartridge. When cart was placed in system, the system would exhibit the click of death symptoms. Installed a missing jumper for the CE* signal for the Program ROM and tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on February 14, 2010, 11:02:15 PM Model: MV2F
Symptom: Video RAM Error Video RAM Error $8000 Written 5555 Read 0000 Replaced 2 bad CXK-5814 SRAM chips and tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on February 21, 2010, 03:18:13 AM Model: MV4
Symptom: Very low audio. Missing audio on slot 4 Recapped audio section to fix low audio issues. Replaced a bad 74LS244 on the top board to fix the missing audio on slot 4. Installed a new battery per owner's request. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on February 21, 2010, 03:53:14 AM Model: MV6
Symptom: Slot 1 not working Repaired 3 burned traces on the top board and tested. It appears the board was powered up wet since the traces that were burned were once that are grounded and next to the power pin on 3 of the 74LS244 ICs. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on March 16, 2010, 09:23:13 PM Model: MV4FT2
Symptom: Graphic corruption, battery corrosion damage Re-mounted the battery to the top side of the bottom board, jumpered 3 corroded traces on the bottom board, sealed up 8 scraped traces on the bottom of the bottom board, then cleaned the top board & slots. Removed a bent pin from slot 2, fixed the bad soldering on a user installed RCA jack connecting a pause button, and replaced 2 missing screws. Tested board. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on March 16, 2010, 09:26:57 PM Model: MV4FT2
Tip: Battery corrosion damage When the battery leaks on the MV4FT2 version of the Neo Geo 4 slot, there are 3 traces that run next to the battery area that control the graphics on the slots that can be affected by the corrosion damage. If this happens, the graphics will come and go, especially when touching pin 56 of the NEO-253 chip at D5 on the top board with a logic probe or oscilloscope probe. The trace from this pin routes to the bottom board and is one of the three traces that run next to the battery area on the top side of the bottom board. These three traces will most likely be damaged and require jumpering with 30ga Kynar wire. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on April 06, 2010, 09:04:12 PM Model: MV2
Symptom: Graphic corruption Board had rodent damage on one of the NEO-257 ICs. Cleaned the board and slots then replaced a leaking battery. Tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on April 25, 2010, 02:54:59 AM Model: MV2F
Symptoms: Vertical lines on both slots Board had a leaking battery. Cleaned up the battery corrosion and jumpered 2 traces between the NEO-257 and the NEO-ZMC2 ICs to fix slot 1. Jumpered a bad trace between slot 2 and the NEO-257 IC to fix slot 2. Installed a new battery and tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on April 26, 2010, 08:56:00 PM Model: MV4
Symptom: Low audio, replace battery Customer requested battery change. Installed cap kit and battery. Tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on April 26, 2010, 08:57:24 PM Model: MV2F
Symptom: Low audio on one channel and lines on screen Battery was leaking. Removed battery, cleaned board, and installed cap kit to fix audio issue. Replaced bad NEO-257 IC to fix lines on screen. Installed new battery and tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on May 12, 2010, 12:53:31 AM Model: MV1
Symptom: Backup RAM Error Board had a Backup RAM Error at D0000, Written 0000, Read 04D0. Replaced bad 74HC32 chip controlling the enable lines. Board then gave a Backup RAM error at D0008. Replaced one 62256 SRAM chip and tested. Board had no audio. Replaced 2 physically broken 470uf @ 16v caps to finish the repair. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on May 31, 2010, 01:05:35 AM Model: MV4
Symptom: Work RAM Error Replaced bad SRAM at location G9 and ran self tests. Audio level was low. Installed audio cap kit and tested. Board would not read any carts. Replaced a corroded 74LS244 on the top board, cleaned the rodent damage, and patched 2 traces. Tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on July 11, 2010, 06:01:34 PM Model: MV1
Symptom: Work RAM Error: Written AAAA Read: AA2A Replaced the SRAM at location H3 and tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on July 12, 2010, 01:48:23 AM Model: MV6
Symptom: No Audio Board had very faint audio when running hardware test. Recapped board and tested. Board had strong audio in test mode but no audio for games. Reset backup RAM and tested. Corrupt backup RAM was causing the audio to not work. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on July 15, 2010, 01:27:49 AM Model: MV4
Symptom: Very low audio Installed audio cap kit and tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on July 18, 2010, 02:37:17 AM Model: MV4
Symptom: Low Audio Installed Cap Kit and tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on July 18, 2010, 03:04:15 AM Model: MV4
Symptom: Low Audio Board would not play hardware test tones. Game audio worked, but was low. Installed cap kit to fix audio levels. Replaced bad SM1 ROM to fix the hardware test tones. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on July 18, 2010, 01:49:06 PM Model: MV4
Symptom: Crosshatch of death Removed leaking battery and cleaned board. Repaired 12 bad traces and tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on July 18, 2010, 05:38:23 PM Model: MV1
Symptom: Tinny sounding audio Cleaned the stereo/mono switch and replaced a bad battery that had started to leak. Tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on July 20, 2010, 02:17:13 AM Model: MV1
Symptom: Stuck on Green Board had the battery already removed and had minimal corrosion damage but still had the crystal and D4990 clock chip with some on it. Cleaned the corrosion, including some bridging the crystal's leads and tested the board. The corrosion bridge caused the crystal to not oscillate. Replaced the missing battery and tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on July 20, 2010, 11:50:04 PM Model: MV1
Symptom: Z80 Error Board was labeled Z80 error but had multiple issues caused by battery leakage, attempted repairs, and rodent damage. Removed an extra Z80 CPU from the BIOS socket and installed the correct BIOS chip. Removed leaking battery, cleaned board, and replaced crystal to fix calendar error. Patched a bad trace going to the cartridge port. Z80 Error had 2 causes. The first was a corroded trace between the NE0-D0 chip, pin 40 and NE0-B0 pin 41. The Z80 Error returned during testing and the IRQ pins on the CPU had bad signals. Pins 36 and 37 on the NE0-D0 read 50 ohms between them. This drove the NMI and IRQ lines for the Z80 CPU. Removed the NE0-D0 IC, cleaned the rodent damage under it, and reinstalled it and the patch to the B0 chip. Tested. The rodent damage corroded the solder on the plated thru holes under the NE0-D0 IC. This corrosion was bridging the 2 pads causing the problems. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on July 31, 2010, 02:29:41 AM Model: MV4
Symptom: Constantly reboots with Calendar Error System was odd in that it would come up with a Calendar Error message then reboot. The reboot was odd since the system should've stayed on the Calendar Error screen. Disassembled system only to find that it worked fine. Tapping the board caused the problem to intermittently return. Resoldered bad connections on the surface mount Work and Backup RAM to fix. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on July 31, 2010, 04:50:09 AM Model: MV4
Symptom: Locks up in Attract mode. Sounds stop working at times. Won't keep high scores. Replaced bad battery to fix score issue. Board would reboot if carts bumped or jiggled. Cleaned the top board and slots then tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on July 31, 2010, 05:10:59 AM Model: MV4
Symptom: No sound Reset backup RAM and then had low volume on right channel and no audio on left. Installed audio cap kit. Replaced leaking battery. Cleaned top board and slots then tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on August 05, 2010, 02:56:57 AM Model: MV4
Symptoms: Carts won't play and Z80 Error Cart in slot 1 wouldn't play and in slot 2 gave a Z80 Error. Board was described as having "shipping damage" and the battery came off from the spot welded leads and bounced around between the boards. DIP switch 8 was on. This is the 'pause' switch which caused the game to freeze upon booting and not play any carts. The Metal Slug cart shipped with the board was dirty. This was causing the Z80 Error. Playing with test carts showed the system had garbled sound effects. No traces were damaged. Swapped out the 74LS244 and 245 chips buffering the sound data. No change. Replaced the YM2610 sound chip to fix the sound issue and tested. Cleaned the Metal Slug cart and tested. Per customer, replaced the battery and missing screws. Replaced 1 PC board standoff that had crossed threads. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on August 06, 2010, 07:30:21 PM Model: MV4
Symptom: Video RAM Error $8000, Written 5555 Read 0055 Replaced bad SRAM IC and tested. Board had low audio. Installed audio cap kit to fix audio issue. Cleaned top board & slots. Replaced 2 missing screws, 2 stripped screws, a broken standoff, and a broken mounting foot. Tested system. The standoff and foot were broken due to insufficient packing in the box. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on August 07, 2010, 12:00:17 AM Model: MV6
Symptom: No audio Could not put board on bench without first contacting customer. The NiCd battery on the board was replaced by a NON-rechargeable lithium battery and the charging circuit was NOT disabled. This was dangerous. Replaced battery with a NiMH rechargeable type, installed Audio Cap Kit, and tested. Replaced one incorrect standoff and reassembled system then retested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 04, 2010, 08:26:23 PM Model: MV-2
Symptom: vertical lines in game Board had a leaking battery that caused trace damage. Jumpered 2 bad traces between the NE0-ZMC2 and the NE0-257 IC, replaced the bad battery, and tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 06, 2010, 09:14:38 PM Model: MV-2F
Symptom: Video RAM Error Video RAM ERROR $8000, Written 5555, Read FFFF Replaced both CXK-5814 SRAM chips. Tested board. Replaced leaking backup battery and tested again. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 06, 2010, 09:16:16 PM Model: MV4
Symptom: Garbled graphics and text The top board had corrosion damage from either a liquid spill or rodent urine. Removed 2 74LS245 and 5 74LS244 chips from the top board. Cleaned the board and checked for trace damage. Installed new chips, repaired 3 traces, and tested board. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 06, 2010, 11:24:29 PM Model: MV4
Symptom: Video RAM Error Video RAM Error $00000005 Write 5555 Read 5557 Replaced bad SRAM IC at K9 and tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 25, 2010, 03:07:41 AM Model: MV4
Symptom: Crosshatch of death Board had a leaking battery but the traces were still OK. Removed the battery & cleaned the residue. Tested traces and found no bad ones. The 74LS138 on the upper board that selects the slots had no signal on pin 4. Replaced bad 74AS244 on the bottom board. All traces were good and all address lines to the carts were good but the system still would not read the carts. Replaced 2 74AS245 ICs interfacing the cartridge data lines on the bottom board and tested carts in all 4 slots. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on October 03, 2010, 04:06:57 PM Model: MV2F
Symptom: Corrupt Graphics Board had a very strange symptom: Character graphics on the left side of the screen and the background graphics were flipped left-to-right on 8 bit boundaries. Text overlay and health bar resources were fine. When the LSPC2 and NEO-B1 chip were tapped, the system would reset. Resoldered pins on both chips to fix the reset issue but the graphics corruption remained. Checked the H signal from pin 109 of the LSPC2 to pin 7 of the NEO-ZMC2 and it was good. This signal is used for flipping graphics elements. Replaced the NEO-ZMC2 IC and tested the board. Per customer's request, installed a coin cell battery mod: Removed the 470 ohm charging resistor then installed a CR2032 batter and holder. Reset Backup RAM and set the time/date. Re-tested board. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on October 10, 2010, 04:41:24 AM Model: MV4
Symptom: Garbage on screen. Dead. Board had battery damage. Cleaned the corrosion from the bottom board and from the connector on the top board. Pinned out all the traces to find out where the damage was... They were all good. Found a broken trace on D4 between the Work RAM and the Backup RAM. Jumpered the trace, no effect. The solder joints and some of the legs were pretty badly damaged by the battery leakage on the Work RAM and the Backup RAM. Removed the RAM, cleaned up the pads, installed new RAM, reinstalled the jumper on D4, and tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on October 10, 2010, 08:53:02 PM Model: MV4F
Symptom: Z80 Error Replaced Z80 IC and tested. Audio levels were low so a cap kit was installed. Board had audio during self tests but not while playing games. Cleared the Backup Memory from within the Hardware Test Menu and tested the system. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on October 17, 2010, 12:42:51 PM Model: MV1T
Symptom: Garbled audio Cleaned Stereo/Mono switch and tested. Board had a leaking NiCd battery. Removed the battery, cleaned up the solder pads, removed the 470 ohm charging resistor and installed a CR2032 battery and socket. Tested board. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on October 30, 2010, 05:31:50 PM Model: MV4
Symptom: Video RAM Error Replaced 1 surface mount SRAM chip and installed an audio cap kit to fix low audio volume issues. Tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on December 02, 2010, 04:21:57 AM Model: MV1FS
Symptom: No video sync Board was covered in an oily residue and had a leaking battery. Cleaned board then patched a bad trace between the LSPC2 and the NEO-IO chips. Removed the 470 ohm charging resistor and installed a lithium coin cell battery and holder. Tested board. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on December 03, 2010, 01:37:25 AM Model: MV2F
Symptom: Video RAM Error $8000 Replaced 2 CXK-5814 SRAMs. Audio had issues. Replaced 2 470uf caps and removed a solder short from the audio amplifier section. Tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on December 03, 2010, 01:37:56 AM Model: MV1
Symptom: Video RAM Error $8000 Replaced 2 CXK-5814 SRAMs and tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on July 29, 2011, 01:13:52 AM Model: Metal Slug 5 (all-in-1 game board)
Symptom: Graphic corruption Resoldered 4 broken solder connections on Graphic ROM C4. Tested game. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on July 29, 2011, 01:14:49 AM Model: Metal Slug 3 (bootleg cart)
Symptom: Dead Resoldered SMT program ROMs and the controller IC for them. Cleaned edge connectors and tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on July 29, 2011, 01:15:57 AM Model: Metal Slug 3 (bootleg cart)
Symptom: Dead Removed shorting solder splashes from an empty program ROM chip location. Resoldered program ROM control chip, cleaned edge connectors, and tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on July 29, 2011, 01:17:53 AM Model: King of Fighters 2003 (bootleg)
Symptom: Dead Resoldered the control IC for the Program ROMs. Fixed one short between the RAM on the cart and the ROM where the wire was to tight going around a sharp pin and the insulation was pierced. Cleaned edge connectors. Game played but with garbled sound effects. Resoldered the sound effects ROMs and their control chip. Tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on July 29, 2011, 01:26:49 AM Model: MV4F
Symptom: Z80 Error Replaced bad Z80 IC. Removed leaking battery, cleaned board, and installed new battery. Cleaned top board and slots. Tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on July 30, 2011, 02:47:31 AM Model: Metal Slug 4 boot
Symptom: Dead Cleaned cart edge connector and tested Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on July 30, 2011, 02:47:59 AM Model: Super Sidekicks 2
Symptom: Graphic corruption Cleaned cart and tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on August 07, 2011, 05:10:34 PM Model: 1 slot (bootleg)
Symptom: Graphic corruption Board came in with a complaint of graphic corruption but was dead. The CPU was a PLCC type and was in a socket. Pulled the CPU, cleaned the severely tarnished legs, and reinstalled. System booted with the graphic corruption. Cleaned the legs on a 27C512 EPROM and tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on August 10, 2011, 11:58:14 PM Model: MV4
Symptom: Low audio and graphic corruption Recapped the audio section of the board and cleaned the top board and slots. Replaced the battery and tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on August 11, 2011, 12:00:07 AM Model: MV4
Symptom: Stuck at crosshatch Replaced connector CN10 on the upper and lower board. Battery corrosion caused it to not make proper connection. Cleaned the top board and slots then tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on August 12, 2011, 11:30:12 PM Model: MV4
Symptom: No audio and graphics corruption Replace NEO-B0 chip to fix graphics corruption. Installed audio cap kit and new battery. Tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on August 12, 2011, 11:31:14 PM Model: MV4
Symptom: No audio. Missing parts Board was purchased as "non-working, no audio" for refurbishing. Replaced missing LM324 op-amp and HA13001 audio amplifier IC. Patched 2 broken traces and installed audio cap kit. Tested board. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on August 16, 2011, 11:54:08 PM Model: MV6
Symptom: No audio Board was bought for refurbishing and resale. It had already been worked on. Replaced 2 incorrect and 1 backwards cap in the audio section. Still no sound. Checked the YM3016 DAC and it's inputs were dead. Replaced the YM2610 and tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on August 20, 2011, 01:46:47 AM Model: MV4
Symptom: Corrupt graphics and lockups Board has been previously worked and has damage from it. BIOS has been replaced with a UniBIOS chip. Replaced the surface mount video SRAM previously installed by the other tech. Patched 2 damaged traces. Board booted to a backup RAM error. Replaced the bad backup RAM. Replaced the UniBIOS with a standard BIOS. Board booted to a Video RAM error. Replaced the other surface mount SRAM and tested. Board had very low audio. Recapped audio section and replaced the battery with a new one. Tested board. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on August 20, 2011, 01:50:26 AM Model: MV4
Symptom: Stuck in watchdog Board has been previously worked on and has damage from it. BIOS is missing. Replaced missing BIOS and 1 missing video SRAM IC. Jumpered a damaged trace and tested system. System booted with a Z80 error. Removed SIP strips used as a Z80 socket from the board. Removed 2 terrible trace patches and tested each trace coming from the Z80. The traces were damaged when the previous tech used a large screwdriver to pry the Z80 from the board. Installed a new socket, new Z80, and 2 Kynar wire jumpers. Board still booted to a Z80 Error. Replaced bad SM1 ROM and retested. Board had almost zero audio when turned up full volume. Recapped the audio section and installed a new battery. Tested board. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on August 20, 2011, 03:34:25 AM Model: Metal Slug 4 cart
Symptom: Graphic corruption. Locks up. Cleaned cartridge edge connector and tested. Cartridge edge connections were too dirty to clean with q-tips and alcohol and had to be cleaned with a pink pencil eraser. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on August 20, 2011, 03:36:09 AM Model: King of Fighters 2000 Cart
Symptom: No audio, severe graphic corruption Graphics were nothing but scrambled colored dots on the screen and were not recognizable at all. Jumpered cut trace where the cartridge was mounted. Reflowed surface mount IC NEO-CMC and tested. Some Neo Geo cartridges have traces that run under the plastic board mounts in the cart shell. These traces can be cut or worn through by the plastic. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on August 20, 2011, 02:58:10 PM Model: King of Fighters 96
Symptom: Corrupt Graphics Cleaned the cartridge edge connectors with a pink pencil eraser and tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on October 03, 2011, 12:10:07 AM Model: MV1F
Symptom: Video RAM Error $8000 Replaced bad CXK5814 SRAM chip and tested. Board had a badly leaking battery. Removed the battery and a 470 ohm resistor from the charging circuit. Cleaned the board and installed a coin cell battery holder and CR2032 battery. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on October 04, 2011, 12:34:32 AM Model: MV1
Symptom: Backup RAM Error Board had a leaking backup battery which ate traces. Removed the battery, replaced 1 SRAM chip, and jumpered 3 corroded traces. Board would boot but was stuck on a green screen - a calendar error. Jumpered a bad trace and replaced the 32.768KHz crystal for the clock/calendar chip and tested. Board would not read DIP Switch 8. Jumpered another bad trace, installed a coin cell battery and holder then tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on October 04, 2011, 12:35:50 AM Model: MV1
Symptom: Stuck on green (Calendar error) Board had a leaking backup battery which corroded the 32.768KHz crystal for the clock/calendar chip. Removed the battery, replaced the crystal, installed a coin cell battery and holder then tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on October 09, 2011, 11:56:01 PM Model: MV4
Symptom: Dead. Nothing on screen. Replaced bad Work RAM, cleaned top board, installed coin cell battery kit, and tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on October 09, 2011, 11:57:00 PM Model: MV2
Symptom: Stuck in watchdog Board came in with garbage on screen and clicking sound, a classic stuck in watchdog problem. Replaced bad BIOS chip, replaced 2 bad SRAM ICs, removed leaking battery from board, cleaned, installed coin cell battery mod, then tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on November 27, 2011, 01:51:09 AM Model: MV2
Symptom: Stuck in watchdog Removed leaking battery and cleaned board. Removed damaged memory card slot connector. Its pins were bent and touching each other. Board was then stuck in Calendar (green screen). Replaced crystal to no effect. Replaced D4990 IC and tested. Removed the 470 ohm resistor then installed a coin cell battery and holder in place of the NiCd battery. Replaced physically broken headphone jack and headphone volume control. Installed a replacement memory card slot connector then tested board. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on December 04, 2011, 04:16:32 AM Model: MV4
Symptom: Work RAM Error Replaced a bad surface mount Work RAM IC and tested. Board then came up with a Video RAM Error message. Replaced another bad surface mount SRAM and tested. Board had poor audio levels. Installed an audio cap kit, replaced the leaking battery with a coin cell conversion kit, and tested. Cleaned the top board, reset the calendar, and tested one last time. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on January 06, 2012, 04:29:12 AM Model: MV2F
Symptom: Cannot control audio on left channel Left channel audio was full blast and couldn't be controlled by the volume slider. Recapped audio section, replaced volume control, replaced leaking battery with a NiMH battery, and cleaned the board. Tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on January 11, 2012, 03:18:18 AM Model: MV4
Symptom: Video RAM Error $8000 Replaced bad CXK-5814 SRAM IC. Board had no audio. Recapped audio section then tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on February 19, 2012, 12:58:09 AM Model: MV2F
Symptom: Backup RAM Error Board had battery leak damage. Cleaned the board. Patched 2 traces on the HC32 IC to fix backup RAM error. Patched 4 traces on the NE0-ZMC2 IC and one on one of the NE0-257 ICs to fix graphic corruption. Jumpered a bad power trace to fix the Calendar Error. Resoldered a popped pin on one of the NE0-G0 ICs to fix slot 2 not working. Removed the 470 ohm resistor from the charging circuit and installed a coin cell battery and holder. Retested board. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on February 19, 2012, 06:43:55 AM Model: MV2F
Symptom: Dead. Stuck in watchdog Board had a leaking battery which damaged the board by eating several traces. Replaced a bad BIOS IC and 2 Work RAM ICs then the board would boot but had graphic corruption and an intermittent Z80 error and no sound. Patched a bad trace on address line A7 between the SM1 ROM and the 6116 to fix the Z80 error and sound problem. Replaced a NE0-257 IC that had a pin corroded through. Patched a trace between the NE0-257 and the NE0-ZMC2 IC. Patched 4 traces between the 2nd NE0-257 and the NE0-ZMC2 IC. This brought most of the graphics back. The output of the NE0-ZMC2 IC was racing on one pin. Replaced the NE0-ZMC2 IC to finish fixing the graphics issue. Removed the 470 ohm resistor from the charging circuit and replaced the leaking battery with a coin cell holder/battery. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on February 19, 2012, 07:46:49 PM Model: MV2
Symptom: Dead. Click of death. Board had batter leak damage. Replaced the Work RAM and Backup RAM. Fixed a bad trace in the battery backup circuit. Board booted with a Backup RAM error. Jumpered a corroded trace to the upper Backup RAM's R/W line. Removed the 470 ohm resistor and installed a coin cell battery and holder. Tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on February 20, 2012, 12:08:43 AM Model: MV4FT2
Symptom: Crosshatch of death Board had no battery leak damage and had already been converted to a coin cell battery. Board would only recognize cartridges when tilted up on its side, otherwise it was stuck on the crosshatch. Board had been previously worked on. Someone replaced the caps and put large blobs of solder on every joint. All of the surface mount ICs on the top board had been reflowed. Used liquid rosin flux and a hot iron to properly flow all the solder on the caps. Jumpered one damaged solder pad. Connector CN10 on the top board had come apart and wasn't fully seating to the bottom board. If pressure was put on the connector the games would boot. Replaced the bad connector and tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on February 22, 2012, 01:48:14 AM Model: MV4
Symptom: Video RAM Error Replaced 2 CXK5814 SRAM chips and tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on February 23, 2012, 11:36:12 PM Model: MV1F
Symptom: Z80 Error Board had been worked on previously and had the Z80 replaced. Board had damage under the Z80 socket. Removed the socket, traced out the connections, installed a new socket, jumpered 2 bad traces, and reinstalled the Z80. Tested board. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on February 23, 2012, 11:59:56 PM Model: MV2F
Symptom: Garbage on screen Board had a Video Memory error which was causing garbage on the screen. When the pins on the chip were touched it would change the screen image drastically. Board had some liquid damage on the Video RAM that ate the trace to address line A0. Jumpered one trace and tested the board. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on March 04, 2012, 05:55:05 PM Model: MV6
Symptom: Calendar Error Could not duplicate issue. Resoldered customer installed clock/calendar crystal. Cleaned board set, installed audio cap kit, and a coin cell mod kit. Tested board. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on March 04, 2012, 10:34:50 PM Model: MV4
Symptom: No audio Board was worked on by another tech and was missing an IC Replaced missing audio DAC. Tested. Board had no audio but did have digital audio working. Recapped board. Board worked but had audio corruption. Replaced bad YM2610 and tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on March 21, 2012, 01:33:53 AM Model: MV4
Symptom: Low audio with scratchy sounds on all slots Recapped audio section to fix low audio. Board not only had scratchy sounds but other sounds would mysteriously drop out. Replaced a bad YM2610 audio IC and tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on March 30, 2012, 12:12:43 AM Model: MV4
Symptom: Stuck on Green (Calendar error) Removed leaking battery. Replaced bad clock/calendar crystal, cleaned board, and tested. Repaired one bad trace on the data lines running under the battery. Installed coin cell battery mod. Tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on April 07, 2012, 12:06:51 AM Model: MV1
Symptom: Graphic corruption Removed leaking battery and cleaned board. Repaired a bad trace on the cartridge riser board. Tested. Installed a new NiMH battery, reset NVRAM, and retested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on April 07, 2012, 12:09:22 AM Model: MV2
Symptom: Graphic Corruption - leaking battery damage Battery was already removed from the board. Removed the corroded NEO-ZMC2 IC. Cleaned the pads and installed a replacement ZMC2. Ran 5 jumper wires to patch bad traces to/from the ZMC2. Ran a jumper from slot 2 to the NEO-257 IC buffering one of the Graphics ROM banks on the cartridge to fix the remaining graphics corrosion. Tested board. Installed a new NiMH battery, reset the backup RAM, and tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on April 15, 2012, 01:31:18 AM Model: MV1
Symptom: Garbled graphics Board had been worked on before, but didn't appear damaged. Removed component lead from under the peeled back cardboard/foam protector on the bottom of the board. It was shorting out traces under the foam. Reflowed the solder joints on a customer installed cap kit. Cleaned riser board/slots. Replaced the NiCD battery as it had just started getting crystalline growth on the negative side. Tested board. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on April 15, 2012, 03:20:16 AM Model: MV4
Symptom: Backup RAM error: Read AA8A Replaced bad SRAM at IC F9 and tested. Board had almost zero audio output. Installed audio cap kit and retested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on April 15, 2012, 11:07:53 PM Model: MV4
Symptom: Stuck on Crosshatch Board had a leaking battery that was already removed before it was shipped in. Cleaned bottom board. Cleaned top board and slots. Patched 3 bad traces that were damaged by the battery leaking. Tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on April 21, 2012, 11:55:29 PM Model: MV2
Symptom: Color RAM error Jumpered corroded trace between pin 51 of the CPU and pin 24 of the the NEO-B0 chip. Board booted with a Z80 error afterwards. Repaired a corroded trace between address line A3 of the sound RAM and sound ROM chips. Tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on April 21, 2012, 11:58:08 PM Model: MV2F
Symptom: Audio issues Installed an audio cap kit, remote battery, and replaced a broken headphone jack. Upgraded the system BIOS to a UniBIOS at customer's request using customer's supplied code. Repaired a broken trace to DIP Switch 8. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on April 22, 2012, 01:40:11 AM Model: Super Sidekicks 3 cartridge
Symptom: Graphic Corruption Game had lines in the background graphics. Resoldered the Graphics ROMs to fix cracked solder joints. Tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on May 26, 2012, 05:19:12 PM Model: MV6
Symptom: Dead, stuck in watchdog Board had burned resistors on the sync line from what appeared to be a faulty monitor connection. A previous repair attempt was made where the resistors had been replaced. Removed a huge wire jumper from the board. Replaced a shorted 74AS244 IC, blown 74LS86 IC, and a shorted CPU. Installed a 30ga Kynar jumper to replace a burned trace. Cleaned the top board/slots. Replaced battery with a Coin Cell kit. Tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on May 26, 2012, 05:21:54 PM Model: MV4
Symptom: Dead. Will not power up. Board had a diode installed between power and ground on the edge connector. This diode was shorted. Removed shorted diode. Board would power up but had low volume issues. Recapped sound section. Board would play but had static in audio and was missing some sounds. Replaced bad YM2610 IC. Cleaned both boards and replaced battery. Tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on May 26, 2012, 05:25:38 PM Model: MV4F
Symptom: Random sounds and memory errors. Won't always recognize carts. Removed leaking battery and cleaned top/bottom boards which fixed sound/cart issue, but the volume was low and would make popping sounds that affected the picture on the screen. Installed an audio cap kit and removed 2 bad mylar caps from the audio output circuit and tested. Board would randomly crash upon warming up. Set all DIP switches to on to force a Work RAM test loop which tests Work RAM and Backup RAM. Board failed with a Backup RAM error after 10 minutes. Replaced bad Backup RAM and tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on May 26, 2012, 05:26:24 PM Model: MV6
Symptom: Stuck on crosshatch Cleaned top board and tested. Replaced battery at customer's request. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on May 26, 2012, 11:31:47 PM Model: MV1
Symptom: Z80 Error Removed leaking battery and cleaned residue off of board. Cleaned slots and tested. Replaced battery. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on July 12, 2012, 02:33:46 AM Model: MV2F
Symptom: Backup RAM Error B240 Replaced bad 74HC32, 2 corroded transistors, 1 cap, and 1 open 22k ohm resistor in the battery backup circuit. Removed the 470 ohm resistor in the charge circuit and installed a coin cell battery kit. Tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on August 12, 2012, 04:58:51 PM Model: MV-2F
Symptom: No audio from slot 2 Checked connections between the slots and the NEO chipsets. Continuity was good. Replaced bad NE0-257 IC and tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 13, 2012, 11:34:31 PM Model: MV2F
Symptom: Horizontal graphical corruption. Graphics had horizontal tears in graphics. Replaced NE0-E0 chip and the LO ROM. Tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on September 14, 2012, 02:21:47 AM Model: MV4
Symptom: No audio Recapped the sound section and cleaned top board and slots. Reassembled boardset and replaced incorrect hardware, missing hardware, and 1 broken mounting foot. Tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on October 03, 2012, 10:58:04 PM Model: MV4
Symptom: Lines on screen and no sound Cleaned top board and slots to fix graphic issue. Recapped bottom board to fix audio issue. Tested. Replaced one broken board standoff, 3 missing top cover screws, and a missing mounting foot. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on November 23, 2012, 10:58:43 PM Model: MV4
Symptom: Backup RAM Error 00D01C0A AAAA EAAA Replaced bad surface mount SRAM IC and tested. Board had low audio. Recapped audio section and retested. Ran board on an extended Work RAM test to check those RAMs. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on December 01, 2012, 05:56:05 AM Model: MV1AX
Symptom: Backup RAM Error Replaced bad RAM 3 and patched 2 corroded traces. Board had the rechargeable lithium battery replaced with a standard coin cell, but did not have the charging circuit neutered. Removed D1, D2, and R10 to disable the circuit. Battery terminals still had 4.38v on it when the board was powered on. Replaced shorted diode D4 and tested. Reinstalled coin cell better and tested power to the Backup RAMs. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on March 04, 2013, 04:00:58 AM Model: MV4F
Symptom: Bad slot, low audio Recapped audio section of the board. Replaced battery with a new NiCd per customer request, and replaced a physically damaged cartridge slot. Cleaned top board and tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on March 04, 2013, 04:02:13 AM Model: MV4
Symptom: Dead. Garbage on screen. Board had some attempted repairs done. Reflowed the solder on 2 surface mount SRAMs that someone had attempted to replace. Resoldered the positive lead on the NiCd battery, recapped the audio, and tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on March 04, 2013, 04:02:48 AM Model: MV4
Symptom: Bad slot Replaced bad slot connector, cleaned top board, and tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on March 04, 2013, 04:04:21 AM Model: MV4
Symptom: Bad slot Slot 1 had garbage on the screen. Cleaned top board, replaced bad 74LS244 at location A4, and tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on March 10, 2013, 10:36:23 PM Model: MV1F
Symptom: Dead Removed foreign substance from a Neo chipset chip and tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on March 10, 2013, 10:40:50 PM Model: MV4
Symptom: Dead. Would randomly boot with graphic corruption Resoldered the PRO-C0 and LSPC-A0 ICs to fix their cracked solder. Tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on March 30, 2013, 05:21:17 AM Model: MV1F
Symptom: Z80 Error Board had severe battery damage. Cleaned battery damage, patched 5 traces on the sound system's SRAM chip, and tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on April 28, 2013, 09:38:11 PM Model: MV4
Symptom: Low Audio. Attempted Repair Damage A ham fisted attempt had been made at replacing the audio caps. They had only replaced about 2/3rds and had damaged many solder pads and plated thru holes. Removed all audio caps and other badly replaced caps. Installed new caps, patched traces, and soldered some caps in on the top side of the board where the plated thru holes were removed. Tested board and found that some sound effects were incorrect. Tested with a known good top board and narrowed problem to the bottom board. Replaced the YM2610 IC and retested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on April 29, 2013, 02:38:44 AM Model: MV4
Symptom: Video RAM Error 8000 5555 5500 Top board had a patched trace from a previous tech Replaced bad CXK5814 SRAM chip. Audio levels were low so a cap kit was installed. Board had lines in the graphics on slot 4. Removed deteriorated foam that was corroding things from the under side of the op board, cleaned the glue/foam residue with solvent, cleaned board and slots, then checked the board traces. Re-ran the existing patch from a via to the chip instead of the slot to the chip as it was much shorter, then patched 2 additional traces. Tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on May 01, 2013, 04:07:59 AM Model: MV4
Symptom: Backup RAM error Replaced both Backup RAM chips. Removed the foam from the underside of the bottom board as it was hardened and was causing corrosion of the board. Patched a corroded trace for the R/W signal to the Backup RAM. Board would boot but only slot 1 was working. Cleaned the top board, patched 8 bad traces, and tested. Board would play, but had incorrect sounds playing. Replaced a bad YM2610 IC and tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on May 04, 2013, 06:26:53 PM Model: MV1F
Symptom: Low audio on right channel Recapped audio section and tested. Installed a coin cell mod on the board and retested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on May 04, 2013, 08:26:32 PM Model: MV1
Symptom: Stuck on green screen Cleaned board. Resoldered 32khz crystal and capacitors. Patched 2 traces to fix DIP switch 1 and 2. Recapped board to fix low audio issues on left channel. Replaced battery with a coin cell mod. Tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on May 06, 2013, 01:42:56 AM Model MV2F
Symptom: Calendar Error Removed leaking battery, cleaned board, patched 6 corroded plated thru holes in the power circuit for the D4990 clock/calendar chip, replaced 1 diode, and installed a coin cell mod kit. Removed damaged memory card slot connector. Tested board. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on May 06, 2013, 01:44:11 AM Model: MV2
Symptom: Video RAM Error 8000 5555 0000 Replaced 2 bad CXK5814 SRAM chip. Removed battery, cleaned the board, and installed a coin cell mod kit. Replaced damaged memory card slot connector with one from a parts board. Tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on May 06, 2013, 01:49:49 AM Model: MV2F
Symptom: Crosshatch of death. Severe trace damage. Board was a parts board purchased in a lot. Someone had done a horrific job of removing the connectors from slot 2 and damaged many traces where they met the solder pads and in-between solder pads. Removed battery and cleaned board. Removed the severely damaged memory card slot connector, installed 2 missing connectors for Slot 2 and tested. Board would not boot cartridges. Patched 1 trace for Address line A9 between the NEO-E0 at position F3 and Slot 1. Board would boot but not play sounds. Patched 2 traces between Slot 1 and Slot 2. Board would play carts in Slot 1 but in Slot 2 they had graphics and sound corruption. Patched 11 additional traces to restore Slot 2 to proper functionality. Installed a coin cell battery kit and tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on May 06, 2013, 10:32:36 PM Model: Shock Troopers 2nd Squad (MVS Cart)
Symptom: Crosshatch Replaced bad P1 ROM. Game played but had no sound. Replaced bad M1 ROM and tested game. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on May 09, 2013, 03:01:14 AM Model: MV1
Symptom: Stuck on green Cleaned corrosion from board as best as possible. Replaced a bad capacitor and crystal in the clock/calendar circuit. Tested traces around the area affected. Tested board. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on June 14, 2013, 01:44:07 AM Model: MV4
Symptom: Slot 3 dead Recapped audio section, cleaned top board, and jumpered a bad trace on the program ROM address bus to fix slot 3. Replaced the battery with a coin cell kit mounted to the bottom of the board. Tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on June 14, 2013, 01:45:03 AM Model: MV4
Symptom: Low audio Recapped audio section, cleaned top board, and replaced the battery with a NiMH type. Tested Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on June 14, 2013, 01:46:44 AM Model: MV4
Symptom: Lines on screen Recapped bottom board, cleaned top board to fix lines, and replaced the battery with a coin cell kit. Replaced missing assembly hardware. Tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on August 19, 2013, 01:38:11 AM Model: MV4
Symptom: Will not play some cartridges Fixed 1 burned trace and 2 gouged traces on the top board. Tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on October 05, 2013, 02:21:24 AM Model: MV4
Symptom: Work RAM error Replaced bad SRAM IC. Tested board. Replaced sound caps and retested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on October 05, 2013, 02:23:00 AM Model: MV1FS
Symptom: System ROM Error, battery corrosion. Removed old battery, cleaned board, and replaced the BIOS ROM. Tested. Repaired a bad trace between the sound RAM and the NEO-D0 chip to fix missing sound. Recapped the audio section to fix a low volume issue on the right speaker. Installed a coin cell battery kit and tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on October 05, 2013, 03:40:38 AM Model: MV4
Symptom: Lines in graphics, random Z80 error, low audio. Recapped audio section, cleaned the top board and slots, and tested. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on October 05, 2013, 05:19:04 PM Model: MV4
Symptom: Memory error, lines and blocks on the screen. Customer requests the installation of a coin cell battery kit and UniBIOS. Replaced 1 bad surface mount Work RAM and 2 bad surface mount Video RAM chips. Replaced the BIOS with a UniBIOS 3.1 (Registered Version), replaced the battery with a coin cell kit, cleaned top board, replaced a bad 74F253 on the top board, and tested. No sound. Replaced bad YM2610 and successfully retested board. Title: Re: SNK Games (Neo Geo MVS / AES) Post by: channelmaniac on October 28, 2013, 01:43:00 AM Model: MV4
Symptom: No audio Board had (poorly) attempted repairs done. A 74AS244 was replaced, the audio caps were half done, and the HA13001 was standing off the board with the mounting hardware missing. Recapped audio section. Replaced poorly installed HA13001 and installed missing hardware. Replaced bad YM2610 to restore audio during hardware tests. Board would play but had no audio. Another tech had replaced the 74AS244 at R1 and damaged a trace. Patched trace between pin 15 of the 74AS244 at R1 and pin 2 of the Z80 CPU at M1. Tested. |