toobin' glitch

kcfreeloader

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My toobin' is doing this weird thing where sometimes the characters dissapear. Sometimes the player, sometimes the computer controled play, sometimes both. It's like the background is over writing them in strips. It kinda hard to explain so i've attached a video. Is it a bad ram chip maybe?
 
Most likely there's a problem in the ttl logic in the object section. Check object rams and go backwards from there.
 
I should add, i removed and sanded the legs of every socketed chip on the board with no difference.

Rattanee: Thanks for the response. How do i check the ram chips or do i just buy spares and replace them one or two at a time until no more problem?
 
That's the one. The board looks fine, but whoever worked on the monitor pcb should be shot. I think they used a blow torch to solder.
 
Don't even get me going on hacky solder jobs... Just got in 5 Williams dot matrix driverboards for pinballs for repair... someone already tried to 'fix' these... you should know these boards get pretty toasty in the powersupply section, and when you combine that with an amateur with a crappy -and- huge soldering iron... let's just say there are just a few traces less on these boards then I'd like...

Anyways, that looks like the ram adressing is messed up for the object roms. First thing I'd try is with the board hooked up and turned on, pull your fingers along the underside of the board on the pins of the ram chips and watch for any static/change. If you see any change, you've found your culprit. Also, if there are any Fujitsu chips on the board, those are always suspect...
 
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