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Old 02-14-2018, 12:19 PM
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TUD1 TUD1 is offline
TheUniversalDave1
 
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Thumbs down Zenith 25LC20 vertical suddenly went crazy

There I was, trying to adjust the dynamic convergence on my newly repaired Zenith 25LC20, and all of a sudden, the vertical deflection lost its marbles. The transformer started making very loud noises, and I can't get full deflection. I thought the convergence board might have something to do with it, so I unplugged it, and the noises went away, but I still don't have full deflection. It didn't start this up until I started adjusting the dynamic convergence, but this chassis has been moved around so much, I find it hard to believe that simply pulling that one board and barely adjusting anything would cause this. I don't know if I caused this, or if, by chance, I decided to do convergence at the same time this dam-ned thing wanted to break.
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Last edited by TUD1; 02-14-2018 at 12:24 PM.
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Old 02-14-2018, 01:30 PM
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I spoke with the previous owner of this TV, and he told me that he completely rebuilt the vertical circuit, even built new vertical integrators.
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Old 02-14-2018, 04:05 PM
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Check the vertical output transformer and see if the convergence winding arced over to the primary winding. Just hope its one of the new electrolytic caps instead, much easier to fix.
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Old 02-14-2018, 04:35 PM
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I was going to try going in there with an ohm meter and test to see if there were any shorts from the convergence plug to the primary of the VOT.
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Old 02-14-2018, 08:30 PM
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teevee teevee is offline
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In some sets the convergence is part of the vertical output tube cathode circuit, disconnecting the board would reduce the sweep size... Easy enough to check on the schematic..
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Old 02-15-2018, 06:49 AM
zeno zeno is offline
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Quote:
Originally Posted by teevee View Post
In some sets the convergence is part of the vertical output tube cathode circuit, disconnecting the board would reduce the sweep size... Easy enough to check on the schematic..
Good point. I dont remember if it was on these BUT some of the Zeniths
had 3 'lytics in the vert out. Usually they caused lin problems
( bottom pulled up) but on one chassis one of them caused strange symptoms.
V out transformers did go in Zeniths, not common but not rare. IIRC
several here have had to change them.

73 Zeno
LFOD !
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