davespicer
Member
After 10 years of procrastination, I finally got around to repairing the HV/deflection boards on a Star Wars cab that's been sitting dormant in my garage for 10 years. The monitor is working great, the AVG board not so well...
What appears to be happening is that any time the beam is moved while inactive, the path is offset upwards. In other words, a right horizontal jump becomes a diagonal up/right. For example, a line of text will have correctly rendered letters, but with the whole line sloping upwards. The BIP screen shows the boxes offset in the Y direction and winding YBIP to its limit doesn't bring them in nearly enough to correct the error.
Here's a quick movie showing the game in action:
http://www.sparcade.adsl24.co.uk/temp/star_wars_sample.avi
Note the sloped text. Given how jumbled the Star Wars logo is, it's possible the error manifests itself differently on larger jumps.
I've tried swapping AVG and vector ROM chips from spare (non-functional) AVG boards with no effect. The AVG output also looks bad on an oscilloscope, making me sure the deflection board is beyond reproach.
I'm about to have a long stare at the schematics and see if I can figure out what could be happening. In the meantime, I thought somebody on this board is bound to have seen something similar and will immediately say, "ahhhh, that's caused by xxxxxx". Does anyone have any ideas?
--
Dave
What appears to be happening is that any time the beam is moved while inactive, the path is offset upwards. In other words, a right horizontal jump becomes a diagonal up/right. For example, a line of text will have correctly rendered letters, but with the whole line sloping upwards. The BIP screen shows the boxes offset in the Y direction and winding YBIP to its limit doesn't bring them in nearly enough to correct the error.
Here's a quick movie showing the game in action:
http://www.sparcade.adsl24.co.uk/temp/star_wars_sample.avi
Note the sloped text. Given how jumbled the Star Wars logo is, it's possible the error manifests itself differently on larger jumps.
I've tried swapping AVG and vector ROM chips from spare (non-functional) AVG boards with no effect. The AVG output also looks bad on an oscilloscope, making me sure the deflection board is beyond reproach.
I'm about to have a long stare at the schematics and see if I can figure out what could be happening. In the meantime, I thought somebody on this board is bound to have seen something similar and will immediately say, "ahhhh, that's caused by xxxxxx". Does anyone have any ideas?
--
Dave
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