Star Wars self-test skewed raster

Brad303

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Help me, Obi-Wan-K-LOV, you're my only hope!

Anyone recognize this problem?

Amp deflection + HV + 25", modern AVG repro.

Game itself draws fine, albeit with a little "overdraw" of the vectors - some of the lines don't quite meet at the same point, but I think that can be tweaked.

I do have a bit of a flicker, too, if that might be related.
 

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It's been a long time since I sold my cockpit, but isn't that screen usually like that? For the red one?
 
It might be. This is my first bona fide Star Wars.

But the manual says it should look like this (note the distinct lack of skewing):

1742193979637.png
 
You can adjust the BIP on the CPU board to get that to align.. However, the BIP adjustment is a bit 'variable' on SW..

Read this post on adjusting BIP on SW logo.. after that, the raster and BIP test screens are less important.
 
You can adjust the BIP on the CPU board to get that to align.. However, the BIP adjustment is a bit 'variable' on SW..

Read this post on adjusting BIP on SW logo.. after that, the raster and BIP test screens are less important.
I had actually read that post a few days ago, and was going to fiddle with BIP on the logo in freeze mode for the overdraw issue (tweaking mentioned in the first post), but would that affect the raster test screen?
 
Yes - XBIP will center it.. and then likely mess up the lettering.. It's a big balancing act, there are tradeoffs.
To me, the logo looking good is more important than the test screens looking good..
I haven't noticed other misaligned vectors once I get the BIP set for the logo to look right..
 
Yes - XBIP will center it.. and then likely mess up the lettering.. It's a big balancing act, there are tradeoffs.
To me, the logo looking good is more important than the test screens looking good..
I haven't noticed other misaligned vectors once I get the BIP set for the logo to look right..
Okay, great. I'll fiddle with it today. And of course, gameplay visuals are far more important than test mode, but one would think calibrated test mode screens would result in better visuals.

I'll just chalk it up to experience-building.

Either that or character-building, but I always hated it when my dad built my character when I was a kid... :p
 
The reason they don't agree is due to aging of the caps in the video section. Particularly the poly caps after the DAC's. (Or at least I've seen it happen with those directly. Others in the video section may be contributing as well.)

As these caps get more and more leaky, the beam 'sags' when longer vectors are drawn. This results in the beam ending up at a location that is slightly off from where it should be. (And as a result, anything drawn after that will be off as well, and you can get accumulated error, depending on what vectors are being drawn and how.)

When they get really bad, the picture will be 'untunable', where any adjustment won't make it 100% correct. But for most games now, it's a matter of spreading out the inaccuracy, so things look 'good enough.' But just be aware, if you see one of these boards, and you've already replaced all of the video section chips, check the poly caps.
 
The reason they don't agree is due to aging of the caps in the video section. Particularly the poly caps after the DAC's. (Or at least I've seen it happen with those directly. Others in the video section may be contributing as well.)

As these caps get more and more leaky, the beam 'sags' when longer vectors are drawn. This results in the beam ending up at a location that is slightly off from where it should be. (And as a result, anything drawn after that will be off as well, and you can get accumulated error, depending on what vectors are being drawn and how.)

When they get really bad, the picture will be 'untunable', where any adjustment won't make it 100% correct. But for most games now, it's a matter of spreading out the inaccuracy, so things look 'good enough.' But just be aware, if you see one of these boards, and you've already replaced all of the video section chips, check the poly caps.

The only thing I've done on the main board set is replacing the AVG chip. Is a recap SOP?

And would that explain my "bendy" As?

1742234520618.png
 
When they get really bad, the picture will be 'untunable', where any adjustment won't make it 100% correct. But for most games now, it's a matter of spreading out the inaccuracy, so things look 'good enough.' But just be aware, if you see one of these boards, and you've already replaced all of the video section chips, check the poly caps.

And/or is replacing the video section chips SOP, too?
 
No. You never want to recap an Atari board. The ELECTROLYTIC caps are all fine, unless they're missing or physically damaged or leaking. Atari used good quality electrolytic caps on these, and they are still good, even after all these years.

The long-vector-sagging issue can be caused by the poly caps in the video section getting leaky. These are not the same as the electrolytics.

Small errors in lettering and other graphics are normal on these. No board is 100% perfect. You can drive yourself crazy chasing every little glitch, many of us have done it. In your case, your picture looks good enough.

The video section is all analog (after the DACs), and everything is 40+ years old. So as everything changes tolerance, every part can contribute to the picture not being razor-perfect. The problem is, you can't always know what causes what. So you only worry about it in cases where it's really bad. There's no point in hacking up a board and replacing a bunch of chips that don't need it.

Yours isn't really bad. (It's actually pretty good, they get much worse.) I would leave that board as it is, and enjoy playing your game.
 
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