Tempest PCB outputs some vectors shaky

joeyoravec

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Wish I had a fancy oscilloscope that could take screenshots, but this will have to do:

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That's measured at the Xout / Yout from the PCB. See the blue vector that looks nice, and see the red vector that is noisy as hell? Predictably, the blue vector is rock-solid on screen and the red vector jumps / shakes around and looks terrible.

What is the analog circuitry doing differently when drawing those two lines? Before I start randomly replacing expensive chips -- what do you think it's doing different for those two lines? The output voltage should be roughly the same so what the heck is the difference??
 

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I wish I could suggest something, mine has shaky vectors and I have yet to figure out a fix. I know it's on the PCB and so far I've replaced the TL082's, 1495's, all adjustment pots and a PCB cap kit. No change after all that.

Please post if you figure it out!
 
I wish I could suggest something, mine has shaky vectors and I have yet to figure out a fix.
Would recommend doing the same sort of oscilloscope test (use 1+ sec persist) to diagnose if it's your board or your monitor causing your shakiness. It's usually the monitor so I was surprised to see the problem on my PCB.

Since this is the test-screen where you adjust position of the triangles with the BIP pot, I'm wondering if the solid lines vs shaky lines are because of different paths through the BIP circuit? I don't quite understand that circuit; still working my way through it.
 
Typically the pots will cause this kind of error, it could also be a flaky lf13201 those switches cause all kinds of problems.
 
Typically the pots will cause this kind of error
They've been replaced. I don't see how a pot could cause one vector to be shaky, but not another, in the same quadrant.
it could also be a flaky lf13201 those switches cause all kinds of problems.
Yeah... I'm suspecting the analog switches, the 1495s, and the polypropylene caps. Anything in the AVG's analog path makes sense; seems like there's a difference between negative-sloping and positive-sloping from that photo.
 
They've been replaced. I don't see how a pot could cause one vector to be shaky, but not another, in the same quadrant.

Yeah... I'm suspecting the analog switches, the 1495s, and the polypropylene caps. Anything in the AVG's analog path makes sense; seems like there's a difference between negative-sloping and positive-sloping from that photo.

Never seen anything like that related to the 1495's filter caps would also be a strong possibility. Maybe there is some noise on one of the 15 volt regulators??

Grasping at ideas.
 
I just fixed DocFrankie's 6100 and with any board I tried it with it had shaky vectors. It ended up being the HV board needed to be recapped, after that and a B+ adjustment the vectors were smooth.

Also might want to try a different AR2 board.
 
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Did you ever find a solution to this? Have two boardsets that have that same problem and I have verified the monitor is not the issue.
 
Did you ever find a solution to this? Have two boardsets that have that same problem and I have verified the monitor is not the issue.

Post a video of what you are seeing. Preferably of the game play, and the test screens (or at least the first screen that says 'press fire and zap to test').
 
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