Ms. Pac dead as a doornail...

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So, a while ago, my Ms. Pac died right during a game.
All of a sudden everything froze and changed color for a couple of seconds and then it was completely black. It appears fully dead on the outside, black screen no sounds.

There is clock signals (I replaced 8A,8B,8C to no avail).

I was feeling all chips for unusual heat. The only one I found suspicious was 7C. I have a working other board-set to compare (this is a hacked Pac board with Ms.Pac attack on it) so I crossed 7F between the boards. No improvement on the dead-board, and the other board worked, although the colors were pretty weird. (not the normal Ms.Pac Attack colors).

I probed 7F with the logic tester and all ports seemed to be low. Checked schematics and checked 3B, no activity on outputs, but also not on inputs, so there must be something wrong further up the line. Haven't had time to do more work.

I just thought it would have been 7F or 3B because 7F was much cooler on the working PCB.

Any suggestions welcome....
 
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Did you check all the basics like +5v across C3, inspect edge connector.
What IC is in question, there is not an ic at 7C??
 
Yes been through all the basics.

You are right I was mistaking, I meant 7F not 7C....sorry (corrected it now in initial post)

7F is the final IC before the video goes to the monitor. The spare board I've loaned from another guy so permanently exchanging it is no option.

I was now looking into examining/exchanging 4A between the boards because that's the next socketed IC. Seems like another PROM or so ?
 
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7F is one of the color proms. It is completely normal for it to be warm. If you need any of the 4 proms I can provide them for $5 each +shipping.
You mentioned having weird colors on the other board, probably pac plus color proms.
Do you have access to a logic probe?
 
Yes I do. That's how I saw no activity on 7F and 3B. I figured if 3B has no activity on the inputs it has to be further up the line.

Yes the colors of Ms.Pac Attack are different (beige scary ghosts instead of blue f.i.).

The thing is that it doesn't even play blind, so I'd expect it to be not just in the video part of the game...

Thanks for your help so far by the way !

Up to now I've been testing inside the cab but that's very clumsy. I'd like to hook it up to a 5V Switcher PSU just for the testing. Can I put the +5V from a switcher over C2 to let it run ?
 
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Measure for +5vdc across C3 or at any rom. If you have 4.95-5.05 there I wouldnt bother with the trouble of hooking up a switcher.
Poke around over at 2R,3R, 2S, 3S and see what you have going on. If any are socketed swap them out. These 161 counters go bad often and can cause video issues or sometimes completly dead board.
Check reset pin on cpu and make sure its staying pulled high.
Btw, yes 7A is another prom. 7A & 4F are both color proms. Your probably barking up the wrong tree there but its easy enough to swap them out if you have some known good ones.
 
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The reason for a switcher was so I could work on the PCB outside of the cab, on a workbench, not as a permanent PSU.
So could I simply hook up the 5V across C2 without damaging any of the power regulating parts, I think so, but I'm not sure.

Thanks, I will try your suggestions tonight !
 
The reason for a switcher was so I could work on the PCB outside of the cab, on a workbench, not as a permanent PSU.
So could I simply hook up the 5V across C2 without damaging any of the power regulating parts, I think so, but I'm not sure.

Thanks, I will try your suggestions tonight !

Ah, hook 5v up across C3. You will also have to hook up 12v over on one of the two diodes over by the sound amp if you want sound. Sorry, dont remember the designations for those diodes.
 
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