#16
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If you disconnect the anode from the CRT and get hi voltage, the CRT is bad.
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#17
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Quote:
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[IMG] |
#18
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I took the second anode lead off the CRT and still no HV. At least I know the CRT is no loading it down. I do have the schematic and when I get time, I will pull the chassis and really dig into it, hopefully this weekend.
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Just look at those channels whiz on by. - Fred Sanford |
#19
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I pulled the chassis today. After partially dismantling the high voltage cage, I found the trouble. A hole had burned into the hv rectifier filament wire. I found another wire in a box of Zenith roundie parts and installed it. I also replaced the 1.5k resistor with a 1k since it is all I had. The high voltage came right back up with no arcing. I put the set back together and checked the high voltage. It was a 30kv presumably because of the resistor replacement. I turned it down to 25kv as recommended in the Sams. Now for a new problem. The horizontal hold will not lock. I suspect the afc diodes because it will operate throughout the range of the horizontal hold control but at center it will not lock in. I have been having trouble up to this point where the horizontal hold would drift especially after being on for a half hour or more and would have to be set further toward the end of the control range to bring it in. I don’t have any diodes to replace them with so I will have to wait until I can order them. I did replace the 6U10 horizontal osc, afc and discharge tube to no affect. I am just glad the flyback did not fail.
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Just look at those channels whiz on by. - Fred Sanford |
#20
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There may be more problems lurking around the flyback transformer. Generally a pulse winding on the fly back feeds the phase detector and if it is open, you will lose lock.
Can you post the schematic focussed on the horizontal afc? |
Audiokarma |
#21
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I got it fixed. It turned out it was a dirty tube socket causing the horizontal hold not to lock. I touched up the convergence and a few other adjustments and now it is back as great as ever. These old sets will keep you guessing sometimes.
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Just look at those channels whiz on by. - Fred Sanford |
#22
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If the CRT lost vacuum you will see a blue purple glow in the neck of the tube.
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#23
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That burned resistor on the 3AT2 socket was a common problem, even when those sets were relatively new.
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