Ms. Pac-Man Problem

Joshmans

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Howdy Hey Guys,
I've got a Miss Pac that's been giving me problems, and I've replaced about near everything on it. I received a working board a few days ago, saw it working, then tried it in my machine and got this.

http://i.imgur.com/Fw4IJ.jpg

Any idea what that means or how to rectify it? The last board did the exact same thing...
 
Howdy Hey Guys,
I've got a Miss Pac that's been giving me problems, and I've replaced about near everything on it. I received a working board a few days ago, saw it working, then tried it in my machine and got this.

http://i.imgur.com/Fw4IJ.jpg

Any idea what that means or how to rectify it? The last board did the exact same thing...

If it was/is a working pcb then I would say that it is your power supply is not putting out the proper voltages.
 
I had the nearly exact same problem. Check the Sync Buss controller near the Ms. Pac-Man ribbon cable connecting the auxiliary daughterboard. Is that doesn't help, try reseating the socketed ROMS as well as the ribbon cable.
 
Was the working PCB running on a switching power supply before?
The board might have been modified to run to the switching power supply.
That would explain why it would work on the other setup and not yours.

You need to check the fuse holder on the MS pacman power supply. Some of the fuse holders work loose and causes oxidation on contacts which causes heat which makes the fuse holder lose contact.

Measure for 5 volts DC is on the board.

Check the edge connectors on the cable. I have seen heat weaken the pins before..
 
That might be a reset problem, some power supplies can do the pcb reset circuit to fail depending on the speed they jump from 0 to 5 volt, you can verify this forcing a manual reset and checking if the pcb start normally. Identify reset cap first (make sure it is not a filter connected to 5 and gnd), then try to short circuit the leads and see if the pcb start. This could be solved modifying the reset circuit, try replacing reset cap to a higher value, 47 or 100 uF for example. Again, please double check you wont short circuit a filter because you would cause a big damage, if your not totally sure, just replace the cap, normally original should be between 1 and 10 uF
 
don't these boards take ac right into them and use diodes to change them to dc. I have a super pac man that is setup like that. If that is the case here then the input voltage should be close to 6 from a switcher power supply.
 
don't these boards take ac right into them and use diodes to change them to dc. I have a super pac man that is setup like that. If that is the case here then the input voltage should be close to 6 from a switcher power supply.

A switcher PS will give you DC not AC, though I never saw it in a Ms pacman, this might be also setup that way...
 
A switcher PS will give you DC not AC, though I never saw it in a Ms pacman, this might be also setup that way...

according to the schematics here...

http://www.arcade-museum.com/manuals-videogames/M/ms_pacman_p4.pdf

On page 18 in the reader pins C,3,D,4 have 7vac applied to them and W,19,X,20 have 12 vac on them.

EDIT:

If this is the case and you are using a switcher you need to bump up the voltage to about 6vdc to get the +5 vdc on the chip at the board.

My suggestion is to measure the voltage on the chips THEN adjust the voltage to get it to the +5 that should be there.
 
Last edited:
I'll chime in here - I suspect your cabinet wiring. Your edge connector, to be exact. Try putting some pressure or wiggling the board connector while watching the monitor in a mirror. If you get signs of life, it's time to replace your edge connector.

Also, if you have a filter board in your cab, take it out. You don't need it.
 
Repinning your harness with a new edge connector is the best thing you can do.

It fixes all kinds of old-connector type issues such as failure to boot, resets, luck-of-the-draw start, etc.

Kerry
 
The issue was the Z80 Sync Bus having problems either via the pins on one board, or from a zip tie over trace fix wires on one.
 
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