q-bert video missing lines ?

djdaveofkc

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Working on a qbert pcb, and it works perfect except for it's missing whole role of line video horizontally across (pics will help explain) I reseated and cleaned a few dirty chips, but not sure where to look for this. Any help is appreciated.
 

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you have a problem in the forground ram? there are 3 ram chips that deal with the graphics, try swaping them and see if the problem moves (one is Horizontal, one is Vertical, and one is for the object type)

E4 (93419) - > Vertical Foreground
E1-2 (93419) -> Horizontal Foreground
E2-3 (93419) -> Object Select

so, if you swap those ie, Vert & Horizontal, and the issue moves, then you have bad ram.
if it does not change, you have something else wrong with the horizontal ram/select area.
 
well, its not a socketed part, its mostly and IC chop or SIP, per the troubleshooting guide posted above.
 
well, its not a socketed part, its mostly and IC chop or SIP, per the troubleshooting guide posted above.

+1

I suggest you do what I did and print out that guide and read it at your your convince. It has lots of great info and I don't own a q-bert yet.
 
i have one qbert in the shop now (done, and fixed, was 100% dead), i have two badly acid damaged boards (prok), and two random sound boards, and i just picked myself up a Qbert (dead but ZERO acid damage) that i need to drive up and get later this month (above a 5 hr drive one way).

so, yeah, lots of qberts around here :)
 
It could be foreground or background. Have a look at this document. It has some good information and what chips to look at.

Looks like the word qbert is separated is SIP71 is the problem with that. There may be more and just fix one at a time. It is on page one of the document above.

Great read Rep 4 U
 
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