Repair and Recovery Techniques
channelmaniac:
Cleaning leaf switches
Arcade buttons are typically one of two types, snap switches or leaf switches. The leaf switches are old school and are preferred by many collectors, but what do you do when the switches don't make good contact?
The switches have metal arms and as long as they aren't cracked, they can be bent back into position. If this doesn't fix the switch the next step is to clean the contacts.
Cleaning the contacts requres a simple, but special tool called a burnishing tool. You can find this at your local NAPA Auto Parts store as it's used for cleaning and polishing points in a distributor on older cars, motorcycles, and other motorized vehicles. They are cheap and are THE PROPER TOOL for doing this.
NAPA calls it an "Ignition File". Item#: SER2153, Price: $2.99
Don't use sandpaper or a sharp kinfe to polish the contacts on the switch, you'll only end up with more problems and with those problems returning sooner. As a plus, this is the same tool needed to clean contacts on old electromechanical (EM) pinball games and slot machines. If you are a collector of old machines, you'll get a lot of use out of this simple tool.
Don't just replace the button with a snap switch type, restore the old game back to it's original shape by simply cleaning those leaf switches!
channelmaniac:
Fixing burnt edge connections
Some arcade games have a BAD habit of burning the edge connectors. Some of the worst culprits are:
Pac Man / Ms. Pac ManPac Man Jr.Pole Position I / II
But it's not too hard to repair the power traces on these boards with some simple copper trace tape. What makes it easier is that the traces are the same on the top and bottom of the board. This allows you to take the tape and run it from the top, across the edge, and to the bottom of the board.
What happens is that the contacts on the harness loosen over the years. The connectors also oxidize and start making bad connection with the board. As the resistance to the current goes up, so does the heat which burns up the connector. Now, on to the repair!
First, take a sharp hobby knife and score a cut across the damaged PC board trace then peel it off the board. Tin the remaining edges of the trace then remove the solder.
Clean the PC board with some acetone or alcohol and Q-Tips then lay down some new copper trace tape. Start by slightly overlapping (1/16 to 1/8") the remaining tinned trace. Fold it over the edge of the PC board and across the bottom of the edge connector the re remaining tinned trace. Smooth it into place with your fingernail.
Put some solder on the top of the trace tape then on the remaining old trace. Bridge the 2 together to finish it. Do the same to the other end of the trace tape.
When finished you'll have a good connection point that will take the current necessary to run the game.
WARNING: To keep this from happening yet again you MUST replace the card edge connector socket on the wiring harness in the cabinet.
Also, if the board is too damaged under the burnt trace you may need to use some extra materials such a fiberglass/epoxy combination to build up the board with sanding to finish.
channelmaniac:
Repairing boards when components have been ripped off.
A customer had a board that was listed as "damaged in shipping" - a chip and a capacitor were "knocked off the board." The repair of this board was complicated in that many of the pads were ripped right off the board along with some traces under the chip.
How do you repair such a problem?
The answer: With patience, a mulitmeter, some tools, electrical tape, kynar wire wrap wire, and a bit of fingernail polish.
First thing to do: clean the board. Remove excess solder from the pads and clean up any flux or other compound from the board.
Next, use a multimeter on the continuity setting to pinout the traces. In other words, where did the pins connect to? This may require following traces on both sides of the board! Use a magnifying glass to check for pins that connect to each other under where the chip body would've been or where a pad for a pin would've been. Use an ultra fine tipped sharpie to mark each location on the board where you can solder a wire jumper to go back to a specific pin on the chip. Don't be afraid of using a sharpie! When the repair is done, flux cleaner will remove the marker too.
If you can't figure out how the chip is wired in, try looking up the datasheet for it on http://www.datasheetarchive.com to see if there are any sample diagrams in it. Or, get a more powerful magnifying glass or a jeweler's loupe to see evidence of where the traces went.
With the pins figured out it's time to mount the chip. Make sure the pins are clean of excess solder on the bottom side where they come in contact with the solder pad. Put a tiny dab of fingernail polish down under the middle of where the chip mounts. Set the chip down on it and align the pins on any pads remaining. Use your liquid rosin flux on the pins/pads that are there and solder the chip using as many pads as you can to hold it in place.
Now use the 30ga Kynar wire to connect remaining pins to where the signals go on the board. Strip the end of the wire and solder it to a pin on the chip. Lay the wire down on the board and use your fingers & fingernails to route the wires as needed. Don't worry if they stick up off the board! Cut it to fit, strip the other end carefully, tin it, and solder it into place.
Now if the other end of the solder connection is too small for you to solder to then try to solder to a plated thru hole. You'll need to gently scrape the coating off to get to bare copper. Tin the copper then solder the wire to the plated thru hole.
If you must solder to a surface mount chip pin then use liquid rosin flux to help keep the solder joints from bridging or going cold. Double check your work to make sure you didn't bridge the solder across multiple legs on the surface mount chip. If you did, use more liquid flux and a clean iron tip to draw away the excess solder. It works like magic. :D
When the last wire is done, straighten up the wires and test. If all works well then clean the board with flux, tack the wires down in various places with electrical tape, and use dabs of fingernail polish to hold the wires and chip in place. When the polish is dry, remove the tape and touch up the polish as needed.
When done, you should end up with something that looks like this AND something that works!
Enjoy!
channelmaniac:
Using ROMIDENT to troubleshoot a board
If a game won't boot enough to run built-in self tests, it can be difficult to troubleshoot. Additionally, if facing graphic corruption, keep in mind that most game boards do not have the ability to test graphic ROMs so how can you tell if a ROM is bad? The answer is easy: use ROMIDENT.
ROMIDENT Download
Newer database of ROMs
WinROMIDENT
Simply unzip ROMIDENT into a directory on the hard drive. C:\ROMIDENT works well for this, BUT before ROMIDENT can be used to ID a ROM image, the chip must be read and the file saved to the hard drive. AVOID putting ROMIDENT in a directory off the desktop as this will require a VERY long change directory command to get to it. For example: c:\documents and settings\username\desktop\romident
To use ROMIDENT, save the ROM image to the directory where it is located, open a DOS prompt, and type in: ROMIDENT xxxxxxx.xxx (where xxxxxxx.xxx is the file name of the ROM you wish to check. The easiest way to do this is to save it on top of the unknown.bin file repeatedly to avoid cluttering up the directory with ROM images.
ROMIDENT will then display the file name, checksum, and the ROM name plus what game it is from. For example:
Code:
C:\DOCUME~1\Owner\Desktop\ROMIDENT>romident unknown.bin
ROMIDENT v2.1
Thierry Lescot, 1998/99.
DAT file revision 3727.
UNKNOWN.BIN [c1e6ab10] = PACMAN.6E from Pac Man (Midway)
C:\DOCUME~1\Owner\Desktop\ROMIDENT>
However, there are times when you get the following:
Code:
C:\DOCUME~1\Owner\Desktop\ROMIDENT>romident unknown.bin
ROMIDENT v2.1
Thierry Lescot, 1998/99.
DAT file revision 3727.
UNKNOWN.BIN [d016686b] NOT FOUND!
Which means that ROMIDENT does not know what the ROM is from. Take the checksum d016686b and run it through the Google or Yahoo search engine. This particular checksum comes back to gg1-7b.2c in the Galaga ROM dumps for MAME.
If the ROM is unknown to ROMIDENT AND is unknown to Google or Yahoo then there are 2 possibilities.
1. The ROM is bad
2. The ROM is from a version of game unknown to the MAME team.
Check another ROM from the board. If it's known then you can assume the unknown one is bad and needs replacing. Use the MAME dumps to get the ROM image needed to replace the bad one.
Enjoy!
channelmaniac:
Using MAME to troubleshoot:
If a board has graphic corruption it can be tough to troubleshoot if the ROMs are soldered in. The easy way around this is to use MAME for troubleshooting.
For example: A Top Hunter game cartridge was sent in for repair with a complaint of "color issues" which turned out to be a graphic corruption problem. Additionally, it was a bootleg. Bootleg carts are generally full of cold solder joints which means every ROM has to be resoldered. This usually fixes bootlegs, but not this time.
The board had jumpers on it and those were verified to be in the correct position by comparing them to a picture of a working cartridge board set. The board had no gouged traces which meant the board most likely had a bad ROM. To troubleshoot this meant desoldering all of the "ROMs" and testing them one by one which is time consuming. These ROMs were actually flash chips soldered to 42 pin DIP adapters and their big square pins meant changing out desoldering iron tips too.
To use MAME for troubleshooting requires:
The MAME softwareA file containing the ROM code for the gameWinZIP or other way to read/write ZIP files
Take the file for the game and play it in MAME to make sure it's working correctly. Next open the ZIP file containing the ROM images and replace the suspect ROM images one by one with a zero byte file. The easiest way to do this is to right click on the Windows desktop and choose New > Text File and give it the file name for the ROM image. Once done, rename the original ROM image name to something else such as adding a ".old" to the end of it then put the 0 byte file into the ZIP archive. Run it in MAME and make note of the corrupt graphics.
If that wasn't the correct graphics corruption then replace the original file and move on to the next ROM image.
For this Top Hunter cartridge this meant doing these steps for the C1 through C8 ROM files. The C7 and C8 ROMs both gave graphic corruption that approximated what was being seen on the game. Desoldering C7 and reading it in the EPROM programmer resulted in a checksum that was incorrect. Replacing the chip with an EPROM with the correct ROM image code fixed the cartridge.
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