pacman plus doubled maze and characters

RiddledTV

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Trying to get a pacman plus working before I return it to a plain pacman.

Before it didnt boot at all, and I replaced the RAM in row 4.
Now it boots and plays but it looks like every other vertical row is a repeat of the row beside it. I get lots of double characters.

I've looked all over at all the screen shots I could find online for troubleshooting, but nothing quite matches this one.

Anyone come across this specific symptom before?

Thanks in advance for looking
 

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Have you checked all the pins on the VRAM Addresser module?
 
I have not, but I swapped out another one and it behaves the same.
I didn't think to try check the socket. Thanks for the suggestion.
 
No dice. Thanks for the suggestion, but all of the pins have good continuity to the main board.

Is there any other ideas for why every other vertical column would be a repeat of the one to the left of it?

It's as if it skips every other line, and instead repeats the previous one.

AACCEEGGII...
 
How are the character roms and their sockets? I cant remember for sure but I think I had a similar issue once and it was a bad 5F socket. Wiggle those roms while its running and see if the screen trys to clear up.
 
Thanks for the suggestion. I just checked continuity from the legs on the top side to the traces on the bottom side of the board. They're all making good contact.

I guess it's possible my ROM is failing, but if that were the case, would the maze also be affected?
 
Pac boards are well known for having shorts on the back sides thanks to bent pins. I'd do a really thorough check on the back for bent pins and shorts.
 
Pac boards are well known for having shorts on the back sides thanks to bent pins. I'd do a really thorough check on the back for bent pins and shorts.

Yes, check the obvious stuff before doing any real troubleshooting. Shorted pins, scratched/smeared traces etc. Areas around the vram addresser card and character roms is where I would start looking first.
 
Fixed

Thanks for the help everyone. I must have scoured the board forever looking for broken/shorted pins and circuit traces. I think the board was in pretty good condition. I ended up finding a tip here:
http://lawnmowerman.rotheblog.com/#playsbut

Plays, Images and Text are 4 1/4 of the left side of a Sprite repeated.

Bad 74LS283 @ 1F (pins 9, 10, 13).

I removed the old chip, put in a socket and new (used) chip. voila working now.

When I first saw that tip days ago, I passed it over because I didn't consider the maze to be a "sprite".
 
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