Ms. Pac-Man No Sound / PROM Failure?

Mauricio

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(this is partly to ask some questions, and partly to help others with a similar issue)

Hey folks,

I have a Ms. Pac-Man PCB that was working fine a few months ago, and I put it in storage (cardboard box with anti-static bubble wrap). I pulled it out over the weekend and it did not have sound. I have it connected to a Retroelectronik JAMMA supergun, not a cabinet. I tried some basic troubleshooting from a forum / web search (e.g. getting static when touching the amplifier solder points means that part is working), but that did not find the problem. All I have is a multimeter, so I couldn't get too much information from the board.

Looking through the Midway troubleshooting guide*, I found all the parts that could result in no sound (and no other issues), and there are quite a few: 1K, 1L, 1M, 1N, 2K, 2L, 2M, 3K, 3L, 3M, 10A (the amp). I do have another Ms. Pac-Man with working sound, so I could start replacing parts to find a failed one. Having never had to desolder before, I just tried swapping the two socketed ICs: the sound PROMs at 1M and 3M. Fortunately that did the trick: I put the 3M from the working board to the non-working one and the sound came back.

Hopefully that will help someone with a similar issue, but now the questions: Is it common for PROMs (and especially these PROMs) to fail? Is there any physical treatment of the board that would make such a failure more likely to occur, or just bad luck?

Last but not least, I would like to get that 3M PROM replaced. Is there someone here on KLOV who sells such PROMs? I tried searching, but didn't find anything relevant. If not, I can go with an eBay seller (looks like $10 + shipping).

Thanks!

- Mauricio

* Link: https://www.arcade-museum.com/manuals-videogames/P/Pacman-Troubleshooting-Guide-Part1.pdf
 
Steph at hobbyroms.com or hyperneogeo (here) or others can help with the replacement PROM.
 
(this is partly to ask some questions, and partly to help others with a similar issue)

Hey folks,

I have a Ms. Pac-Man PCB that was working fine a few months ago, and I put it in storage (cardboard box with anti-static bubble wrap). I pulled it out over the weekend and it did not have sound. I have it connected to a Retroelectronik JAMMA supergun, not a cabinet. I tried some basic troubleshooting from a forum / web search (e.g. getting static when touching the amplifier solder points means that part is working), but that did not find the problem. All I have is a multimeter, so I couldn't get too much information from the board.

Looking through the Midway troubleshooting guide*, I found all the parts that could result in no sound (and no other issues), and there are quite a few: 1K, 1L, 1M, 1N, 2K, 2L, 2M, 3K, 3L, 3M, 10A (the amp). I do have another Ms. Pac-Man with working sound, so I could start replacing parts to find a failed one. Having never had to desolder before, I just tried swapping the two socketed ICs: the sound PROMs at 1M and 3M. Fortunately that did the trick: I put the 3M from the working board to the non-working one and the sound came back.

Hopefully that will help someone with a similar issue, but now the questions: Is it common for PROMs (and especially these PROMs) to fail? Is there any physical treatment of the board that would make such a failure more likely to occur, or just bad luck?

Last but not least, I would like to get that 3M PROM replaced. Is there someone here on KLOV who sells such PROMs? I tried searching, but didn't find anything relevant. If not, I can go with an eBay seller (looks like $10 + shipping).

Thanks!

- Mauricio

* Link: https://www.arcade-museum.com/manuals-videogames/P/Pacman-Troubleshooting-Guide-Part1.pdf

The sockets can get corroded/ oxidized and prevent them from working , as well as the legs on the chips. Most people replace the sockets when they are corroded and clean the chip legs. You could try cleaning them with an eraser... I also found a post where someone cleans his chips with tarnex. It could be that reseating the chips is all it needed as that could have cleaned some oxidation off... or they could have just gone bad. Point is try cleaning them first before ordering some new ones.
 
Did you try to put the non working PROM to the other pcb? If that is the culprit, you will not have sound....
 
Did you try to put the non working PROM to the other pcb? If that is the culprit, you will not have sound....

Ah, I should have mentioned that... yes, I did swap them and the problem swapped as well, so it is definitely the 3M that isn't working. (for some definition of "definitely")

Is this a common problem, especially without any obvious cause?
 
(



Hopefully that will help someone with a similar issue, but now the questions: Is it common for PROMs (and especially these PROMs) to fail? Is there any physical treatment of the board that would make such a failure more likely to occur, or just bad luck?







Thanks!



- Mauricio



* Link: https://www.arcade-museum.com/manuals-videogames/P/Pacman-Troubleshooting-Guide-Part1.pdf


Nothing special you can do just bad luck. Corrosion and bad sockets often are the issue with these but as you stated not in this case apparently.

I've fixed a few hundred various game boards in the last 5 years and I've had maybe 5-7 of them bad bipolar proms.
 
Nothing special you can do just bad luck. Corrosion and bad sockets often are the issue with these but as you stated not in this case apparently.

I've fixed a few hundred various game boards in the last 5 years and I've had maybe 5-7 of them bad bipolar proms.

RE: Corrosion: Both of these ICs and their sockets look pretty good, still shiny. I also checked voltage on both, and it was good, for what that is worth. I can see some darkening on the legs of the main masked ROMs: 5E/5F and 6E-6J. Apparently masked ROMs (as opposed to EEPROMs with windows) are more likely to corrode. So far they are still working though, though I suspect their legs will break if I ever need to take them out.

Interesting that you have seen so few bad PROMs. I figured this must occur with some frequency since there are quite a few people selling (unmodified) programmed Pac-Man ICs.
 
when I say bad PROMs I meant the small 82Sxxx bi-polars that you were mentioning in the sound circuit.
That said I dont often run across bad EPROMs either, though definitely more than bad 82Sxxx chips.

With the exception of mask roms as you mentioned which are often falling apart.

-brian


RE: Corrosion: Both of these ICs and their sockets look pretty good, still shiny. I also checked voltage on both, and it was good, for what that is worth. I can see some darkening on the legs of the main masked ROMs: 5E/5F and 6E-6J. Apparently masked ROMs (as opposed to EEPROMs with windows) are more likely to corrode. So far they are still working though, though I suspect their legs will break if I ever need to take them out.

Interesting that you have seen so few bad PROMs. I figured this must occur with some frequency since there are quite a few people selling (unmodified) programmed Pac-Man ICs.
 
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