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Sony KV-32S40 Horiz. Drive Problem

This set is proving to be a tough fix. I picked it up in the trash a while ago, and when I first tried it everything seemed to work fine. After about half an hour though the picture went very dark and shrunk in on the sides. The problem is permanent now and will not go away. All voltages on the secondary of the flyback - HV, CRT filament, etc. are about 30% below normal but the B+ is a solid 136V. All voltages from the power supply are good, and there are no bad caps... it seems like the horiz. drive signal isn't strong enough. I tried replacing the horizontal driver transistor as well as all electrolytics in that area, and fixed some cold solder as well, but it made no difference. Any ideas?

Reply to
Chris F.
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Did you resolder the horizontal drive transformer?

Mark Z.

Reply to
Mark Zacharias

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After you run the set for a few minutes, turn it off and see how hot the horizontal/flyback transformer is. If it is scorching hot, there may be a shorted turn on the transformer, that will cause what you are seeing..

Reply to
hrhofmann

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Sometimes a failing/ed non-polarised capacitor in the flyback area causes that problem

Reply to
N_Cook

I think if that were the case, the horizontal output transistor would have died in short order. Of course, the bad solder at the drive transformer, which is VERY common, can and does kill the output transistor also; I was just thinking the OP had been lucky up to this point.

Mark Z.

Reply to
Mark Zacharias

NP tuning caps? Cold solder flyback pins?

--
Live Fast, Die Young and Leave a Pretty Corpse
Reply to
Meat Plow

Try the G2 rectifier diode and it's feed resistor you will probably find tracking marks under the components.

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Reply to
John Ferrier

Resolder all power semiconductors which are mounted on heat sinks or the metal frame of the chassis.

Stefan

Reply to
Stefan Heimers

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