Ms Pac Aux Board Possessed by Evil

[jlpmauldin]

Sorry in advance for another Ms Pac-Man related question...

I have a Ms Pac that shows the static image below when I power up the game.

Steps taken so far:
- Replaced all sockets on Aux board with new ones
- New ribbon cable
- New 40 pin socket on main logic board (where the ribbon cable plugs in)
- Verified all eproms on aux board (U5, U6, and U7). They all checked out at ROMident. *I originally thought these were non-standard hacks. Sorry. Ninja edit fixed*
- Removed and measured both electrolytic capacitors on Aux board: Good
- Removed and measured the 4 ceramic capacitors on Aux board: Good
- Verified all board connections at every pin on every component on the aux board per the schematic. All good. No broken (or bridged) connections.

I have removed the Z80 processor and the ribbon cable and plugged the processor into the
main logic board. As expected, the game comes up as playable Pac-Man with some sprite weirdness.

I have taken a known working aux board, plugged it into the new ribbon cable, and the game comes up and plays normally.

I have swapped all 8 chips from the bad aux board with the 8 chips from the good aux board. The good aux board still boots up normally, the bad board still refuses to do anything except show the same static image.

I looked at the supply voltage on the board with my scope. I see a stable 5V (4.94V as measured with my DVM).

I'm pretty much out of ideas. Before I perform an exorcism (or just admit defeat, buy another board and get on with my life), has anyone seen this problem? Any ideas? Thanks!

https://drive.google.com/file/d/1-TlithBMdS5C3EfzF7g2Eoda06sCtngQ/view?usp=sharing

 

[gamefixer]

I'd hack that sucker to a 4-in-1 and call it a day.

http://arcade.souzaonline.com/

 

[behrmr]

Yep. Or single rom mod it to me pac

 

[gamefixer]

the 4-in-1 is easy enough to do. Plus it give you both games at fast and slow, freeplay with attract and high score save!

 

[brzezicki]

if you need a known good aux board I"m pretty sure I have a few spares.

$25.00 shipped to USA

 

[brzezicki]

sorry my apologies, I was not able to validate any of my aux boards as my test ms. pacman board has decided to stop working.

-brian

 

[jlpmauldin]

Thanks to everyone for the interest and helpful comments.

sorry my apologies, I was not able to validate any of my aux boards as my test ms. pacman board has decided to stop working.

-brian

No worries! Already got other parts on the way. By the time this project is over, I'll have lots of spare parts.

I think I may use some of the spares to try the 4 in 1 hack. Time permitting so we'll see. I've got a whole other Ms Pac to restore after this one... and several other games... so many.

Still kinda bummed I never figured out the problem with the first aux board. I may try to replace the ribbon cable socket again, just in case I messed up an old trace or something.

 

[mecha]

most likely a bad ribbon cable, as the CPU is on the aux board.

I don't know for 100% certain where replacements can be obtained, but as noted in other posts above, you have a lot of different options.

 

[Cmndr Brain]

 

[demogo]

> Ms Pac Aux Board Possessed by Evil

I hear that Catholic priests are good for things like that?

 

[jlpmauldin]

most likely a bad ribbon cable...

I figured that too. I bought a new one that works great with my good aux board, but not with the cursed one.

I hear that Catholic priests are good for things like that?

I tried a little ceremony but it didn't work.

https://drive.google.com/file/d/1e3N0EoudkuxmdUs4IkSKN3kamhVCKBGH/view?usp=sharing

 

[Jr. Pac]

What do you mean "speed up" hacks on the daughterboard? The standard speedup hack is done on the motherboard at 6F and the "hot pursuit" full-speed-up versions don't use the daughterboard. The only daughterboard mod I know of is the U7 for Ms Pac Attack mazes.
If you have some kind of bootleg speedup it may be that they also require a matching custom row 6 and don't match up.

I'd for sure replace/reburn the U5/U6/U7 with stock just to at least rule that out

 

[jlpmauldin]

What do you mean "speed up" hacks on the daughterboard?

Here is the ROM ident info for the ROMS that were installed:

https://drive.google.com/file/d/17kHmeqpjo7VW6W2-j0O61ezl8zi0nEpW/view?usp=sharing

I guess I misread this information originally. I see now that this probably just means the ROMS could work with the speed up hack, not that they have necessarily been altered themselves.

When I install these on the good aux board, the game works and Ms Pac goes really super fast. Also, coining up instantly starts a 2 player game (no chance to press 1UP or 2UP).

Maybe I should burn a completely clean ROM set and try it. Not sure if I have a spare 2716 around at the moment. Thanks for the help!