Q&A Thread

[channelmaniac]

If you have questions relating to the threads in this forum section, please post them here and not in the individual game repair threads.

Thanks!

RJ

[dlfrsilver]

Final Fight :

Ok i got 3 boards for this one. There is one who should work but it says on self test WORK RAM NO GOOD.

Can you help me by telling me where this Work Ram is located on board ? thank you !

[Peri]

            For such an error ,there might chances that the Boot-ROM is faulty as per my experience. Since you have got 3 pcs,then it is better that you first swap them in order to pin point that which of the portion i.e Upper or lower portion is having problem.

[channelmaniac]

That error points to the A board - the bottom board in the 3 board stack. It's one of the 256k SRAM ICs.

The problem is that there is no documentation for which of the many 256K SRAM ICs is bad. You'll have to swap them out one by one until you find the bad one.

RJ

[dlfrsilver]

Hi guys, after testing, it appears the A-board (game board) are all fine (all 3), i tested them with my Mercs B-board PCB and they all works.
The pb is on the B-board (motherboard), one of the 256k SRAM is dead or maybe more as channelmaniac said.
I have picked their references, HM65256BLSP-10 and M5M5178P-45.
I suppose from what you said Channelmaniac that the problem is with HM65256BLSP-10 right ?

Also, very sad news, i got today 2 PCB in good condition (no trace cutted as far as i saw), but they are DEAD

one is Bad dudes vs dragon ninja, a flat black covered chip with 10 pin marked 'RCDM - I1   86' has been smoking under my eyes !!!!
and the second is robocop, nothing appears on screen, it's like the vsync is ON, with nothing more.....

any idea on what is RCDM - I1 86 will help me, i can't find on google what kind of chip it is, resistor, capacitor, i don't know.

[channelmaniac]

A pic would be very helpful

[dlfrsilver]

no pb ! i do that

[bibisama]

Hi !
just discovered this place and i thaught it might be a good place to ask for some help about my 2 faulty MVS NEO-MVH SLOT1FZS

here is some pictures





One of the slots had a damaged bios (burned ?)


I replace both bios on both slots with a unibios 2.3 and I now have a picture, but it seems it's lacking some graphics in the first slot and the second one misses graphics too AND have vertical black lines all over the screen.

first one



Second one


Both slots have been washed and inspected, I did not find any evident bad traces (looked quickly)

Any ideas ? Thanks !

[westec1]

One of our site moderators Channelmaniac has a repair topic on these types of games

Here is the link

http://newlifegames.net/nlg/index.php?topic=152.0

Wes

[bibisama]

Yep, I saw
Just wanted to know his thaughts about it, I'm not really an expert, maybe he could help me out on this.
thanks

[bibisama]

Hi
The second slot doesn't have any black lines anymore after cleaning again.
One of the slots had corrosion due to battery leaking. I removed the battery and cleaned the corrosion a much as I could but no still no background graphics.
With the original bios installed I had garbage screen with the click of death.
I don't know where to look at and I don't know how to test the chips (I only have a digital multimeter)
Any help would be much appreciated, thanks !

[channelmaniac]

Hmmm...

That chip is burned. You'll need a replacement for it.

As for the missing graphics, you'll want to check the corrosion affected area for damaged traces. Also look closely at the board for scraped traces on the bottom side that need patching. It's a common problem on those smaller boards.

RJ

[bibisama]

thanks for your answer
I replaced original burned bios with a unibios 2.3
I saw on your logs that missing background appeared also when the 74ls244 chips are dead. I only have 74ls245 chips on my board, is it worth it to replace them ?

I looked very closely for damaged traces or hits on the board but did not find any, could they be UNDER some chips near the battery ?
thanks

[channelmaniac]

It's possible but I don't remember what traces are around that battery on that particular board.

Double check for any scrapes or scratches on the board. It doesn't take much to cut through a trace.

74LS244 are buffers and are typically used for buffering address lines. The 245 chips are latches and are used to latch data onto the data bus. I doubt one of those would cause that problem but you never know.

[bibisama]

Ok, i'll check one more time.

If I don't find any evidence of damaged traces, where should I look for next ?

[channelmaniac]

Bent pins on the cartridge slot... and make sure the vertical board is plugged into the bottom board. It's possible that they could be partially unplugged.

[bibisama]

Hi
I saw on one of the boards that a component is missing



Could you tell me what this component is ? it's labelled "PC" on the board

What should I use instead of this missing component ?
thanks

[channelmaniac]

It's a simple bypass cap used for filtering +5v... it's a .01uf monolithic capacitor.

If it's missing you probably will have zero problems. It's not a part that does anything drastic. It just filters the 5v line a bit.

[bibisama]

Thank you !

I looked very closely with a magnifying flass and a multimeter for bad traces but did not find any

Vertical board and cartridge slot seems good too.

Any more ideas before I give up trying to repair those things ?

[porchy]

Hello,
Hope this is the right place to post this, if not I apologise.
I have an original X-Multiply PCB running on the Irem M81 hardware. Ive been having a few graphical issues with it and with a quick inspection noticed that 3 of the legs on a rom were heavily corroded just about gone!
I am able to burn a new eprom but this is where I get stuck.
The M81 B board where the roms are located has a jumper switch located at the end of each rom bank with the options of MASK or EP. Currently this is set to MASK and im guessing that EP means eprom?
So, can I just simply swap one of the maskroms out for an eprom or do I have to replaced them all with eproms and change the jumper over to EP?

Hope you can help because I cant find anything about these boards out.
Let me know if you need any more information

Thanks very much

[channelmaniac]

The easiest thing to do would be to check the traces going to the jumper with a multimeter to see what the difference is between the 2 settings. You might have to modify the traces going to the single socket.

RJ

[porchy]

ok, this is what Ive got
when set to MASK (pin 1 & 2), pin 1 goes to number 2 on the chip socket, this is empty when a maskrom is fitted
pin 2 goes to number 22 on the chip socket

when set to EP (pin 2 & 3), pin 2 goes to number 24 on the chip socket (#22 if the 28 pin maskrom is fitted)
pin 3 goes to ground.

Im not too well clued up when it comes to pinout meanings so am a little lost with it.

also forgot to mention earlier, the maskroms fitted are 23c1000 and are 28 pin.

thanks again for your help, your information on this site has already proved very valuable to me on a couple of occassions.

[channelmaniac]

OK,

These should be 28 and 32 pin devices.

Mask = 28 pin equivalent to HN62321 which is VERY similar to a 27C301 EPROM.

EP = 27C010 type EPROM which is a standard JEDEC pinout.

The 27C301 is almost the exact same pinout as a 27C010 - pins 2 and 22 are swapped.

Check to see if your EPROM programmer will program a 27C301. If it will, check pin 2 on the board (Pin 2 as related to the whole 32pin socket) to see if it is grounded. If it is then the 27C301 will be a direct replacement and you can leave the jumper in the Mask position.

If not, use a 27C010 and swap pin 2s and 22 by building an adapter. To do this, take 2 chip sockets. Bend out pins 2 and 22 on the top socket then use some tape and some wires to jumper the pins 2 and 22 around.

Go to http://www.datasheetarchive.com and pull down the data sheets for HN27C101 and HN62321. In there you will see what I'm talking about.

HN62321 is the 28 pin MASK ROM and is equivalent to what you have in there now as a mask ROM.
27C101 is the JEDEC pinout 1Mb EPROM
27C301 is the non-JEDEC pinout 1Mb EPROM which is (mostly... look at pin 2!) mostly pin compatible with the mask ROM.

RJ

[porchy]

I have been learning a lot about eproms and also getting to know my eprom burner a bit better. I have come across a few instances, mainly in forums and once for myself, where certain address pins on the eproms allows access to different areas of the eprom.
For example, on my Irem board I asked you about in my previous posts, I have to read the 23c1000 as a 27c512 eprom, covering pin 22 so it doesnt make contact, and running a wire from GND to pin 22, dump the data, then run the wire from VCC to pin 22 to get the second half of the data. My question is, how do I find out what address pins activate these different areas? Ive checked some datasheets but not 100% on what im looking for really. This is more for curiosities sake than functional at this time but when I get interested in something my tendancy is to run with it obsessively.

Thanks for any help you can give
Jon

[channelmaniac]

Every address line doubles the space on the EPROM for storing data. The highest address line doubles it from 512k to 1024k. What you are doing when grounding it is to access the lower 512k space then the upper when you are tying that line to Vcc (+5v)

You should've used a couple of sockets and some wire to rewire it to fit into a 27C010 or 27C301 pinout and read it as a whole 1Mb EPROM.

RJ