Ms. Pacman... fails to boot fully, has weird graphics issue.

thegnome

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Ms. Pacman... fails to boot fully, has weird graphics issue.

Ok, so I just bought a Ms. Pacman that I knew had some issues, but I have no experience with board repair and would love some pointers on a) what could be causing this issue and b) either a course of action to repair it myself or a reference to someone who is good at doing so. I don't mind buying tools to work on it myself as long as it's not something that will require more monetary investment than a board would cost... especially if it's something simple.

Now, having said that... here's the issue I'm facing. When I turn the machine on the marquee lights up and the monitor comes on and I get partial graphics on the screen (see pic #1), however the board never displays a self-test and there's no sound output aside from a humming that I assume is from the marquee lights or monitor. Now, the harness has been hacked a bit (see pic #2) and the edge connector has been "repaired" by jumpering from the harness to the trace on the board. I have also noticed that the diodes at D7 and D8 have either been reflowed or replaced at some point.

Could any of this be causing the issue at hand?

Thanks in advance guys.
 

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When I got my first game..Pac-Man..I found this site very useful.

http://lawnmowerman.rotheblog.com/

Also with pacs.. try making sure the edge connector is seated firmly as well the socketed chips.
 
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Yes, that site is excellent. Also check out the schematic and troubleshooting guide which can be downloaded off of the listing for Ms. Pac on KLOV.

Start by cleaning up the board, including the edge connector. Carefully remove and reseat each socketed chip, making sure to do it slowly and applying even pressure. Some of the IC legs on Ms. Pacs are pretty brittle at this point, so take it easy.

You also want to check the fuse block at the bottom of the cab for blown/missing fuses, and clean the fuse contacts.

Once you've done all of this, one of the first steps of Ms. Pac board troubleshooting is to remove the Z80 processor from the daughterboard connected to the mainboard via the ribbon cable, and put it in the slot where the ribbon cable connects to the mainboard. Depending on its behavior at this point, this will let you know on what board you have the problem, and takes the daughterboard out of the equation.
 
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Ok, so bypassing the auxillary board allows the game to boot up and display the attract mode, without sound and slightly corrupted graphics [title screen graphics are messed up but gameplay graphics are fine with exception of ms. pac herself which has glitchy animation]. I pulled out all the socketed chips and checked for broken legs and oxidization and cleaned up any that I found [no broken legs, but some oxidization on daughterboards]. Reconnecting the auxillary board causes the same problem as before... blank screen with one random graphic in the bottom-right corner.

This would mean that the issues are mostly confined to the auxillary board, correct? Is there anywhere to purchase a replacement ribbon cable (to rule that part out)?
 
If you guys get stuck, ask Riptor he knows them boards better than anybody.

A more accurate statement would be that I know them better than I know any other boards.

Your graphics problems are because your running mspac 5E & 5F without the aux board. I would replace the ribbon cable since these are usually the problem. Were you using the Z80 from the aux board?
On the sound issue first make sure the volume pot is turned up. Also check and make sure your speaker wires are connected. If you narrow it down to a board problem the first thing I would check is the proms at 1M and 3M.
 
do you hear any sorta "pop" from the speakers when you turn the game on? You could have one or both 12VAC fuses blown.

Oh, +1 as to what Riptor said about the ribbon cable.
 
Sound issue is sussed out. Seems the hacking of the wiring harness wasn't just confined to the edge connector and coin-door. Unfortunately, I can not find a replacement ribbon connector locally to get that further narrowed down. I did however pull the current cable from the machine and tested continuity on all the pins and a couple are iffy and pin #40 is completely dead. I tried jumpering pin #40 with some excess wire but still no dice. Went ahead and ordered a ribbon cable a few minutes ago, so hopefully it'll be here early in the week so I can get that figured out.

Now, I'm just going to have to go over things and fix all the wiring "creativity" that a previous owner has imbued the machine with... and begin repairing the buttons and joystick. This lil lady has lived a rough life in some seedy places...
 
Ribbon cable arrived in the mail today... and VOILA! She lives! Now I just need to rebuild the joystick and it's on to cosmetic repairs.

Big thanks to riptor for not only pointing me in the right direction to getting this old gal operational, but also for shipping out the parts in a super timely fashion.
 

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