G05-802 jittery and partial deflection problems

DogP

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Hey,

I've got a G05-802 in my Omega Race cockpit that's REALLY jumpy, especially vertically (almost looks like rolling from a mis-adjusted vertical hold on a raster), as well as being a small image in all axes (maybe half size). It also looks to be only on the bottom half of the screen, though it looks like the entire image is just shifted very far down, so I don't know that it's truly partial deflection.

I checked the output from the board on my oscilloscope and it looks fine, so I'm pretty sure it's the monitor, and since I had my HV probe handy, I checked the HV and it looks good, so I'm thinking my real problem is with the deflection board.

The frame mounted transistors test fine, and I also checked Q606, Q607, Q706, Q707, and they seem fine, though I've read several places that they frequently test fine, but fail in operation, so I'm thinking of replacing these just to make sure that's not my problem. I also tested Q605 and Q705, and both seemed fine. The caps also tested fine w/ my Cap Analyzer.

One thing I did notice is that C504 (I think?) seems to hold a charge, so it throws sparks when I discharge it... not sure if this is normal. Attached are some pics... the first is one of the entire monitor (to show size), then the others are zoomed to show the image. And no, I didn't move the camera, the vertical blur is a picture of what's actually happening.

Any ideas?

Thanks,
DogP
 

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The +y amplifer is not working. The components most likely to fail in that circuit are Q608- 2n3716 and Q606-MPSU07. Especially Q606. Try switching it with Q607 and see if there is any change. Cold solder points on that board are common. Reflowing the entire deflection board is a good idea.
 
Thanks... it's mostly original, with just a few small components that appear to have been replaced. I did reflow the solder joints, but wiggling connectors and stuff didn't seem to make any difference, so I don't think it's connector related anyway.

I'll try swapping Q606, but shouldn't it be with Q706? IIRC Q606, Q706 are the same and Q607 and Q707 are the same.

Thanks,
DogP
 
Thanks... it's mostly original, with just a few small components that appear to have been replaced. I did reflow the solder joints, but wiggling connectors and stuff didn't seem to make any difference, so I don't think it's connector related anyway.

I'll try swapping Q606, but shouldn't it be with Q706? IIRC Q606, Q706 are the same and Q607 and Q707 are the same.

Thanks,
DogP

Q706 is for the x amp. I show it on the schematic as being a MPSu57.
 
Hmm... I see that in the schematic as well, yet looking at the symbols, clearly Q606 is PNP and Q607 is NPN, so something's not right, and it says both X and Y channels are identical. I'll pulll the board and verify this shortly. But yeah, swapping X and Y should be fine, and if I see my problems switch to the X axis, then :) .

Thanks,
DogP
 
Okay... I swapped Q605-Q607 with Q705 to Q707, as well as swapping the frame transistors between X and Y, and still no change. One other thing I noticed is that the spot killer seems to be kicking in quite a bit, but the input seems fine on the scope.

Any ideas? I've got several of these monitors here, but I think they're up in my attic, but I'll probably grab one of them next and see what happens on a different monitor altogether, and then swap boards to be sure I'm chasing the right problem.

Thanks,
DogP
 
Okay... I swapped Q605-Q607 with Q705 to Q707, as well as swapping the frame transistors between X and Y, and still no change. One other thing I noticed is that the spot killer seems to be kicking in quite a bit, but the input seems fine on the scope.

Any ideas? I've got several of these monitors here, but I think they're up in my attic, but I'll probably grab one of them next and see what happens on a different monitor altogether, and then swap boards to be sure I'm chasing the right problem.

Thanks,
DogP

Full solder reflow would be my next step.
 
Yeah, I already reflowed the solder joints before, but it didn't make a change... but it's okay now.

I sorta cheated, but when I was digging around for another monitor, I came across a spare chassis, which I popped in and looked pretty good, so I reflowed some solder joints that looked bad (to prevent future problems), then adjusted everything, and it looks great. The spot killer problem ended up being the game board needing adjustment, but after all that, my Omega Race cockpit is working :).

So, I'll tag this chassis and stick it in my repair later pile ;) .

DogP
 
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