Battlezone jumpy X vectors

hackbar

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I have a Battlezone with jumpy vectors on the X axis. Here's a video:

This seems to only happen in game, not test. The only problems I see in test are a short edge on the left side, and maybe slightly messed up copyright symbols? In game, most things have bad X coordinates - the moon, horizon, crosshairs, rader, etc. It's like it's missing a bit in the X resolution.

I've tested all the ROMs, RAM, and swapped out the aux board. No errors in test. I've written some short programs to test the vector generator, and can't reproduce it myself.

Any ideas what's causing this, or things to check next? It's strange this is only in game, and the test screen doesn't seem to reproduce it.
 
The vector ROMs are probably original and have become flaky. I'd try burning some EPROM replacements if you are still running the originals. Fresh RAM chips wouldn't hurt either if the originals are old (since you've tested, they must all be socketed.) I've had RAM pass the self-test but then obviously fail during gameplay. Also, ensure there are no mathbox errors posted in test (could be a contributor, but doesn't explain everything in the video.)
 
Yeah I've already changed chips, that was my first thought.

No math box errors in test.
 
is it banding the jumpy x in certain y areas? moon and tank area is bad but score area is good
 
do not know too much about battlezone but asteroids I am fairly familiar with and a few things I would consider to look into on an asteroids would be scaling counters and adders
 
It's only in some vectors. but it doesn't seem to correlate to regions.. The score is good, but the extra lives near it are drawn too close together. So I don't think it's a window issue.

I had thought it might have been a scaling issue, so I wrote a simple program to using the SCALE opcode. I couldn't get it to reproduce it though, either using the analog or digital scaling.
 
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