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"Bad C RAM 1" Message on Pac-Man Screen

cerkit

cerkit

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After successfully getting power to my cabinet, I am now met with an error message on the screen:

Arcade-Pac-Man_Bad_C_RAM.jpg


It displays this after going through what looks like a self-test (YouTube video), displaying all of the sprites in the top left corner of the screen, then filling the screen with animated garbage text, and finally stopping on a black screen with this message towards the top.

I have removed all of the socketed ICs one at a time and cleaned them with a pencil eraser, but that didn't work. The board looks good. I did a cursory check for broken traces using a flashlight, but I didn't see anything. It doesn't appear that anyone has modified this board. However, I'm not sure that the ROMs are original.

Arcade-Pac-Man-ROMs.jpg

Is this issue possibly related to the 2114 ICs? I saw where I can buy them on ebay. I could easily buy and replace those.

Is it possible to troubleshoot the RAM ICs with an ordinary multimeter? I also have a hobby oscilloscope (25MHz), signal generator, and a cheap USB logic analyzer (not a logic probe). Not much in the way of tools, I'm afraid.

Thanks for any help.
 
It's a bit overkill, but you can use your scope to look for stuck address or data pins on the 2114s. Just need to grab the pinout and see which pins are which. They should be pulsing, so anything stuck high/low or floating is suspect. This isn't a guarantee that the RAM is bad, just that there's a signal issue going in or out. Could also be a part of the glue logic, so you'd want to follow the bad signal to the source to see where it falls apart.

However, I might suggest starting with replacing the 2 sockets that the daughter cards plug in to. Over the years, these get stretched out and start to cause all sorts of weirdness.

Do you have a good desoldering setup? Something like a Hakko Fr300 will make the job a ton easier!
 
98pacecar said:
However, I might suggest starting with replacing the 2 sockets that the daughter cards plug in to. Over the years, these get stretched out and start to cause all sorts of weirdness.


Do you have a good desoldering setup? Something like a Hakko Fr300 will make the job a ton easier!
Click to expand...
No, just a solder sucker, solder wick, and a soldering iron. I could probably pull it off with the wick.
 
Your video is the normal Pacman boot sequence. When it gets to the end, it was rebooting.

The error message and symptoms are consistent with a bad 2114 at 4P. You can swap the Rams around to see if the message changes and to other symptoms to confirm the chip is bad and not a trace or another upstream chip. Or just replace it if you have another one.
 
Last edited:
Sjlewis78 said:
Just curious if you were able to fix this. :)
Click to expand...
I got the replacement RAM today (2114N). I started by replacing the bad RAM chip as mentioned above. That just gave me a blank screen. The monitor is powering up because I can see the orange glow at the base.

So, I tried replacing all of the RAM. No luck. I still just get a blank screen.

Any ideas?
 
You went from an error message to a blank screen? That's very odd.

Since you took the board out. Check the edge connector. On pac games it's common for them to get worn out.
 
Sjlewis78 said:
You went from an error message to a blank screen? That's very odd.

Since you took the board out. Check the edge connector. On pac games it's common for them to get worn out.
Click to expand...
I also took out the little board that sits above the RAM (video board?). When I replaced it, I bent a pin. Then I bent another pin. Now it's back in there correctly. I may have ruined it by bending the pins too much.
 
The VRam addresser, you still shouldn't get a black screen I don't think

Those usually have an extra brown socket under the main pins. You can remove the extra socket if those are the pins that you bent. You can take that socket off and either put on another one or just put it directly in.
 
I did find a bad trace on the RAM chip in question. It was on the back of the board.
Arcade-Pac-Man-Broken-Trace.jpg

I repaired it by soldering it to the via that the original trace connected to.

Arcade-Pac-Man-Fixed-Trace.jpg

I then checked the continuity from the pin on the RAM to the various points along the board that I could find.

Still no luck, though. I still have a blank screen. I had my speakers wired up wrong from when I removed the harness. Once connected, they make a crackling sound when starting that lasts about 15 seconds and fades off.

I also re-checked all of the fuses and they are OK.

The edge connector looks good and the wires seem to be strong.
 
OK, I got the screen to come on finally. I had to wiggle the edge connector once it was connected to the board.

I am now getting the boot up screen (sort of - it cycles through ghost sprites), but it seems to restart each time it finishes and I hear a clicking sound in the cabinet somewhere (sounds like it's coming from the coin door) and the speaker pops. I no longer have static from the speaker when starting.

I have a cocktail cabinet.
 
Those pesky edge connectors. Lots of things can cause the game to reboot constantly. Id start at the 4 program roms to make sure they are good
 
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