U2000 - Dead Horizontal Section Repair

zenomorp

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U2000 on the bench. No signs of life. No ticking, no sounds, nothing. Report was it was working and then died with a burning smell. Quick testing revealed the power supply was working but the horizontal section was not energizing. Nothing visually looked bad. No burned spots, burned components, etc. Testing the normal causes (HOT/Q703/Q708/R760/R765/etc) revealed that R760 was completely open. This will prevent Q708 for turning on and that will prevent the horizontal section from turning on. I didn't see the exploded chunk until I removed it and turned it over. It's supposed to be 100-500 ohms (depending on the revision of the board), so I stuck a 500 ohm replacement in there since that's what most of them are. That brought it right back to life. Got the B+ set to 117vdc, everything adjusted, and there were no other issues.

R760 and R765 are one of the most common failures on the U2000 and U5000. If you've got a dead U2000/U5000, always check R760 and R765.
 

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