What's Wrong with this Ms. Pac?

[sc1103]

One of my friends has a good quality Ms. Pac machine, but it recently stopped working.  According to them, it boots up and then there is just garbage on the screen, with a blinking zero in the upper right.  I thought it may be the Z80 (but im an arcade newb) so does anyone know what I need to fix this and where to get it?  If you guys need pics Id be able to get out there tomorrowish.

Thanks for any help

[RayB]

It can be any number of things. Bad RAM, dying capacitor. Power supply problem or simply something came loose. (Did they move the cab recently? Did they start using a really long extension cord?)

At least you know it's not a problem with the monitor.

[sc1103]

It can be any number of things. Bad RAM, dying capacitor. Power supply problem or simply something came loose. (Did they move the cab recently? Did they start using a really long extension cord?)

They haven't moved the thing since they got it and have been plugging it in through a surge protector the enitre time.  Any suggesstions on how to narrow down the problems? 

Thanks again
If I post pics can that help at all?

[RayB]

Step 1 is always a visual inspection. You never know when something could have just come loose on its own, or a little furry critter may have decided to make the cab its home.

Step 2 or 3 is measuring voltages from the power supply.

Step 3 or 2 is putting the game into test mode if it has one and see what the results are.

Step 4 ...?

[General Zod]

You might want to check out this site, as it's helped me in the past, and might just do the same for you.

http://users.erols.com/mowerman/pacfile.htm

It covers quite a bit on troubleshooting your pac boards.

[tbombaci]

Gently re-seat the ribbon cable to the daughter PCB. (you will need to remove the Sync Bus card to get to it)

If that doesnt work, gently remove the Z-80 from the daughter card and stick it in the slot where the ribbon cable is plugged into. Re-seat the sync-bus card and turn on the game. If all is good, Pac-Man should boot with odd shaped characters (ghosts and Pac) The game should play as pacman.

If this is the case, the ribbon cable is probably toast. A new cable is about $10.

-Tom

[MonitorGuru]

Check this page and compare screen shots:
http://www.arcadegameover.com/troubleshoot/pactrouble1.html

I'd hazzard to guess the following, in order:
1) Bad video ram. Swap (to diagnose) and then replace the 2114/9114 chips in row 4
2) Bad Sync Buss Controller board, pins, socket.
3) Bad Z80-chip, socket
4) For Ms.Pac: Bad daughter cable, sockets (on both ends)

Regarding the video ram: If the chips are TI brand chips (texas logo) be VERY careful. They have the weakest legs and break VERY easily. You may even notice a break with one still in the socket. Press against them and you might just find the offending one without even removing.  All the other brands I've seen (GTE, National Semiconductor, etc...) have much stronger legs in Pac boards and are much easier to swap to diagnose.

[sc1103]

Thanks for all the help so far guys...Ill hopefully be goin out there soon to see what I can do and Ill report back

[RayB]

Keep in mind that insufficient voltages levels will cause problems that look like bad RAM, etc...