Ms Pacman ghosts transporting from home

schwaggs

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Problem is that for the first 10 minutes the game is running, the ghosts that are in their home will randomly flash all over the screen for a second or three, then stop somewhere on the screen and move slowly over walls. They will even move off the edge of the screen to appear on the other side.

Eventually they the transported ghost will get back to normal. I think usually when a power pill is eaten, not totally sure what other events make them get back to normal. They will also get back to normal after you die.

They only transport when in their home. If they are in the grid, they act totally normal and never transport.

What I have tried:

Recapped the board
ROMs from another board
Removing MS pac board
VRAM and Sync bus controller from another board

I couldn't find any repair logs that mentioned this specific issue so I replaced the chips with similar issues from Mike's page and the repair logs I found:
Replaced 1E and 2E 74LS161
Replaced 1F and 2F 74LS283
Replaced 3H and 3F 7489

The only thing on the DR bus I have not replaced is the pull-up resistors.

Anyone had this one before or have a suggestion for me?
 
Also forgot to mention that I replaced the CPU and ROM sockets and cleaned the chip pins.

Could this be a flaky CPU?

VRAM Addresser socket?
 
The 284 and 285 sockets are known to be issues, so I would replace those. While those may not be causing the issue, at least you'll know those are NOT the problem. I doubt it's a CPU issue, but that is quick and easy to swap. Have you pulled the RAM, cleaned the legs, etc.?

Scott C.
 
I have cleaned the legs on all socketed chips. I'll try the 284 and 285 sockets next. Thanks
 
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