GO7 B+ Issue

iggins

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The B+ on one of my GO7's is measuring ~170V, and shutting down. I swiped the potentiometer, and the voltage went back to 120V, and the monitor came back on (scrolling and washed out colors?). I powered down and back on, and it was back at 170V. Adjusting the pot doesn't fix it again.

The transistors measured OK.

Following the flowchart, it seems that I may need to replace IC 501, though I haven't removed transistor X701 yet.

My question is - is this just a bad pot, or does this behavior indictate that I should order an IC 501?

Thanks for any tips. I just want to have the parts I need available before I start working on the board.
 
cap kit would be my next move and check for cold solder while you have it out also check folr hairline cracks around the flyback and power section.
 
What other work have you done to this monitor? Caps? New flyback?

I don't think the pot is the issue.

As said before, check for cracks in the PCB.

The VR is metering okay?

Check X901 and X902.

R908 should be checked, too.
 
It's been working fine for about a year. Cap kit, flyback, and width coil (done by me).

I did pull it out the chassis and examine for solder opens and bad solder joints, but I didn't find anything obvious.

Thanks for the tips! I'll do some more detailed debug tomorrow or this weekend.
 
cap kit would be my next move and check for cold solder while you have it out also check folr hairline cracks around the flyback and power section.

Troubleshooting would be my next move, vice shotgunning parts at the problem.

Remove X701 and retest.

Most likely the regulator 2SC1106 has failed, and needs to be replaced. IC501's do go bad, but not that frequently. The flow chart is a guide, and is NOT gospel.
 
cap kit would be my next move and check for cold solder while you have it out also check folr hairline cracks around the flyback and power section.

This. If it went from 170 to 120 back to 170, that indicates a cold solder joint or ten. The scrolling and washed out colors indicate caps. If you do caps, you'll probably need a new flyback, too...
 
Troubleshooting would be my next move, vice shotgunning parts at the problem.

Remove X701 and retest.

Most likely the regulator 2SC1106 has failed, and needs to be replaced. IC501's do go bad, but not that frequently. The flow chart is a guide, and is NOT gospel.

I would have pulled x701 and then vr if caps didn't work. If I'm not mistaken one or two caps can cause the B+ to spike so since he is going to replace them he should replace them all to adress the other problems he is having.
 
Just to follow up, I pulled X701 and the monitor worked fine. I then replaced the regulator and re-installed X701. It seems to be solid now.

Thanks for the replies.
 
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