Q*bert's having a seizure...

elekTRONarcade

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Hey guys,

I recently picked up a decent-shape Q*bert for $50, and after some fiddling, I was able to revive it...mostly. When it comes up, it will do one of four things:

1) Load into the test screen, which while readable, has some glitched characters (20% of the time)
2) Load into the test screen, then quickly switches back and forth to the title screen and is unresponsive (25% of the time)
3) Loads into the normal title screen and will play, with a lot of various graphical glitches
(Q*bert logo is shifted...the bottom half and top half are switched...missing characters/glitched characters on the Level display screen....various glitches on the gameplay screen (wrong characters, missing characters, missing pyramid, level screen elements/artifacts left onscreen etc) (40% of the time)
4) Loads up with just random characters/elements scattered across the screen (15% of the time)

I've gone through the various repair logs and troubleshooting guides found with Google, and if I went by their recommendations, I'd pretty much replace every IC on the board. I've replaced the caps, bypassed a broken trace/broken harness wire straight to a test point on the trace path and pulled/cleaned all the socketable ICs to no avail. So ultimately my question is, is there one particular thing that could cause this huge myriad of issues? Like maybe an under/overvoltage situation or something else?
 
The first thing you should do is replace the test switch which is going bad. Its a normally closed switch so when the contacts get dirty it will jump back and forth from test mode.
 
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