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-   -   Zenith 25LC20 vertical suddenly went crazy (http://www.videokarma.org/showthread.php?t=270136)

TUD1 02-14-2018 12:19 PM

Zenith 25LC20 vertical suddenly went crazy
 
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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.

TUD1 02-14-2018 01:30 PM

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.

DavGoodlin 02-14-2018 04:05 PM

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.

TUD1 02-14-2018 04:35 PM

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.

teevee 02-14-2018 08:30 PM

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..

zeno 02-15-2018 06:49 AM

Quote:

Originally Posted by teevee (Post 3196208)
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:smoke:
LFOD !


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