Asteroids screwy graphics

BeagleBoy

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While waiting on parts for my dead monitor, I decided to hook my asteroids up to my oscilloscope, and see if I had any video (it plays blind).

On the scope, you can make out objects, but they're pretty screwed up. Flipping it into the test screen, the cross-hatch pattern is pretty much missing. The dip-switch 0's are drawn normally, but 1's cause weird offsets.

I'm not really sure where to begin testing components, so if anyone can point me in the right direction, I'd greatly appreciate it.



-Jim
 
The issue looks digtal to me. I'd start on the input side of the DACs and work backwards, into the X&Y position counter section.
 
I spent this evening working on the G05-801 (SUCCESS!!), so I haven't had a chance to test anything on the pcb yet. But I did snap some much better images of what the game is doing.

As you can see, there's a lot of strangeness. In addition to generally scrambled shapes, the letters are way too big in a lot of places and the saucers are huge.

Cross-hatch screen with no dips set:
wpid-IMG_20110825_220100.jpg


Cross-hatch screen with dips 5, 6, and 7 set:
wpid-IMG_20110825_220129.jpg


Attract mode:
wpid-IMG_20110825_220201.jpg


Saucers:
wpid-IMG_20110825_220230.jpg
 
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