Ms Pac Man dead. Vram Addresser?

David P

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I went to fire up my Ms Pac Man last night and it wouldn't do a thing. I looked in on the PCB and gave it a nice once-over to check for bad/blown components. I noted 2 things.

1. When I tapped the ribbon cable going to the secondary board, a couple of times the game "beeped".

2. The Yellow 104 Capacitor on the VRam addresser board looks like shit. LOL I just had that board off a few weeks ago to reflow some of the solder points and reseat the board. I didn't notice the cap then, but I wasn't necessarily looking either.

Ok so, could a bad cap on that board cause the issue? I no longer have my Pac Man game to swap the board (if it's on the Pac PCB, now I don't recall). Secondly, I see the cap says 104 "something", LOL as in 104 152, or 104 I5Z. I can't make out WHAT exactly that component is. Can someone clarify the part? I'd like to hopefully drop into Fry's to pick it up, as mail order would just be ridiculous for the stupid thing.

Thanks!
 
104Z = .1uf 50v
Thats not your problem. I would start looking at sockets or the ribbon cable. Make sure the Sync bus card is seated good, things like that.
 
Hey Riptor, is that a ceramic cap? I don't offhand recognize all the types, but electrolytic's are easy to spot.

I'll dig into the game and recheck the cable seating. Thanks

LOL btw, that leads me to wonder where I can pick up a stupid .1uf cap. Radio Shack only carries a Metallized Polyester Film Capacitor, and I'm not seeing jack at Fry's. Now to find a laundry list of parts I don't need...
 
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Yeah its a ceramic cap. Its a standard cap and if you have any junk boards laying around you can pull one off it. Virtually every arcade pcb uses them. I have plenty if you cant find them locally. Radio shack probably sells a ceramic disc assortment that should have them in it.
 
Yeah that one will work. That cap is not causing your problem. You can clip it off the board completely and it will still work.
 
I'll keep checking into more board or ribbon cable problems. Maybe I'll reflow the connector solder points, and I'll recheck the seating.

Meanwhile, the cap just bugged me as I was scanning the board. I suppose I'll make that secondary to the main problem.

Thanks again and again.
 
If that cap blow up, your pcb has probably received high voltage from anywhere, might be a HV leak in the flyback of the monitor, or a missing cable accidentally, those capacitors don´t usually blow up, if this is what happened, half or more of the pcb ic´s might be burnt. Do you have a scope? if not, start touching ic´s to see they are not hot enough to feel the burn in your hand. But definitively the cap is not the cause of the issue. As riptor sayed, pcb should work either with or without any of those caps, any you can see a lot of them in most pcb. Sorry for my enghlish..
 
The screen is completely black; though once I got two random symbols at the top of the screen (I can't remember what they were now). Then of course were the odd, loudish, beeps when I was messing with the ribbon cable.

I would HOPE that if the isolation transformer were leaking that it would blow the fuse, but then again, if it's a small leak, then it may slip past it and fry other parts...

Oh, and no scope. All my handiwork needs to be done with a multimeter...
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OK I had to call a friend that was there when we fired it up (technically the games at his house while I 'make room' here (so I won't get my tail in trouble with a particular woman). Anyway, he confirmed what I was thinking. The game ONCE showed 2 White Pac Man symbols at the top of the screen, facing left. They were also smaller than normal.

Omarale, I could always unplug the monitor to stop any possible further damage, but is there a particular set of IC's that would be hottest? The best I can think of would be the ones with the heatsinks in the lower right corner, or do most put out quite a bit of heat? Before trying, leave the game on for what, 10 minutes first?

Lastly, the power supply has been changed out to a switcher, so I'd hope that those don't leak AC like the older power supplies. Once I did have an MCR in my TRON game leaking like a sieve and the game was screaming like a bansee when turned on. It was the 2 suitcase caps at the bottom.
 
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Are the voltages on the board good? Particularly the 5V at the ICs?

If you suspect the ribbon cable, you could disconnect it and move the Z80 cpu from the aux board onto the main board where the ribbon cable was previously plugged in. The game should then run normally as Pac-Man. (but with messed up sprites IIRC)
 
Sorry Delroy, I edited my previous post, not realizing you'd posted.

Ok so to test the board, just disconnect the Ribbon Cable, and move the Z-80 over? At least I'd get SOMETHING on screen if the ribbon cable/solder points/connector is causing the problem...?
 
If that cap blow up, your pcb has probably received high voltage from anywhere, might be a HV leak in the flyback of the monitor, or a missing cable accidentally, those capacitors don´t usually blow up, if this is what happened, half or more of the pcb ic´s might be burnt. Do you have a scope? if not, start touching ic´s to see they are not hot enough to feel the burn in your hand. But definitively the cap is not the cause of the issue. As riptor sayed, pcb should work either with or without any of those caps, any you can see a lot of them in most pcb. Sorry for my enghlish..

I am sorry to say, but this has nothing to do with your problem. The monitor has no way of putting voltage into the game board. You do not need to unplug the monitor. Unless some retard wired the monitor directly to the game board, they are on totally different power circuits.

Verify that you have the correct voltages available on your game board. (ie +5vdc & +12vdc)
 
I am sorry to say, but this has nothing to do with your problem. The monitor has no way of putting voltage into the game board. You do not need to unplug the monitor. Unless some retard wired the monitor directly to the game board, they are on totally different power circuits.

Verify that you have the correct voltages available on your game board. (ie +5vdc & +12vdc)

Sorry I must disagree Dokert, I have seen many rgb output stages, gals, peel even eprom and cpu´s burnt for that reason, even the moment the arch was happening, unfortunately. Unless you are reffering to NANAO or other circuits where rgb ground is isolated of the flyback ground, there are many chasis with a very simple circuit where even an internal short circuit in the flyback could transfer HV to pcb game. DAVID P, I hope this would not be the case, but I strongly recommend to get a scope if you want to solve the problem, as for the symptom you refer cpu is not proccesing and this would come from many different ic´s. I assumed you had tested 5 and 12 volt if you mentioned that you changed the PS to a new switching PS. Try to place the Z80 in the ribbon cable socket to see if there is a bad contact on it. That is a good beginning. I am sure you´ll find a good help in the site delroy has posted, it is an excelent source for your case. Regards
 
I've got to get back out TO my game. Like I mentioned, I have to clear space so that um, a woman here, won't boil over when I bring ANOTHER woman through the door; and to bring her in non-functional would not go over too well.

Unfortunately I'm away for a short stint and can't get back to the Ms till tomorrow at the earliest (yes it's killin me not to tear into it).

Omarale, I've never looked into a proper scope. Got a decent one in mind? Then again, even if I DID buy one, I'm not trained on how the heck to use it... =\
 
Tektronics is better but sorry I thought you had knowledge to use a scope, it´s not that easy and you need to have a wide electronics basis. I think you will only be able to follow the tips we would suggest based in what you found, if this don´t work, i recommend you to send the pcb to any repair service. Try first with the info of the site mentioned above and let us know what happens.
 
Sorry I must disagree Dokert, I have seen many rgb output stages, gals, peel even eprom and cpu´s burnt for that reason, even the moment the arch was happening, unfortunately. Unless you are reffering to NANAO or other circuits where rgb ground is isolated of the flyback ground, there are many chasis with a very simple circuit where even an internal short circuit in the flyback could transfer HV to pcb game. DAVID P, I hope this would not be the case, but I strongly recommend to get a scope if you want to solve the problem, as for the symptom you refer cpu is not proccesing and this would come from many different ic´s. I assumed you had tested 5 and 12 volt if you mentioned that you changed the PS to a new switching PS. Try to place the Z80 in the ribbon cable socket to see if there is a bad contact on it. That is a good beginning. I am sure you´ll find a good help in the site delroy has posted, it is an excelent source for your case. Regards

Omarale,

If that were the case then he wouldn't have much of any video on the screen now would he? ;)

I must disagree with your diagnosis too.

The op should disconnect the ribbon cable (NOT BY PULLING THE CABLE TO REMOVE THE HEADER FROM THE SOCKET) from the main board and plug the CPU that is on the daughter card in the socket on the main board.

If the game plays Pac Man with the Pac character looking like it is walking on its lips then the board is fine. It'll do that with the Ms Pac character ROMs installed and running with the Pac program ROMs. (Remember that the Ms. Pac program ROMs are on the daughter board that you unplugged if you followed what I said in the previous paragraph.)

If it works like that then replace the ribbon cable and try hooking the daughter card up again. The ribbon cable can be hard to find. I keep a big stash of 40 pin IDP connectors here just to remake cables as needed.

RJ
 
Omarale,

If that were the case then he wouldn't have much of any video on the screen now would he? ;)

I must disagree with your diagnosis too.

The op should disconnect the ribbon cable (NOT BY PULLING THE CABLE TO REMOVE THE HEADER FROM THE SOCKET) from the main board and plug the CPU that is on the daughter card in the socket on the main board.

If the game plays Pac Man with the Pac character looking like it is walking on its lips then the board is fine. It'll do that with the Ms Pac character ROMs installed and running with the Pac program ROMs. (Remember that the Ms. Pac program ROMs are on the daughter board that you unplugged if you followed what I said in the previous paragraph.)

If it works like that then replace the ribbon cable and try hooking the daughter card up again. The ribbon cable can be hard to find. I keep a big stash of 40 pin IDP connectors here just to remake cables as needed.

RJ

Ok you are right, I might have exaggerate the diagnosis because he mentioned that a cap was burned, but I said probably ( not sure ), may be because of I don´t have a good english speach, I might have been misunderstood, sorry for that, obviously you can´t diagnosis something you can´t check, and that´s why I never would say : ¨that´s your problem for sure¨ I hope he would have found the problem of the pcb. Regards
 
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