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Philips 32PT563S w/ Horizontal Short Issue

I am looking for help to find short that develops in the horizontal section of a Philips 32PT563S37G (Chassis L01.1UAC-7638).

When the TV was first going out, it would be difficult to turn on. It would take several attempts at turning on to get it to stay on. It started with the right side of the screen wavering along the edge and somewhat folding over on itself. As the TV would be turned on repeatly it would eventually settle down and stay on and be ok. Then finally one day the TV died and the HOT (horiz output transistor) shorted out (zero ohms across all junctions). This wavering on the edge of the screen only happens on the right, never on the left.

I've replaced the HOT twice with a NTE2636 - can't locate a true replacement for the BU4508DX - I can only get the BU4508AF which doesn't have the Re and damper diode built-in. I have replaced every electrolytic capacitor in the TV that's on the main board (not any on the SSB or CRT yoke board), along with two PNP (BC32725 & C557B) & two NPN (BC33725 & C547B) transistors. The electrolytics were all replaced with the same manufactuer - I got them all from Mouser.com. And yes, I did replace the capacitor 2455 along with the NPN/PNP transistors nearby.

While I had the HOT out of the TV I tried checking the flyback (part # OV2076) windings with an ohm meter. I used a diagram for a HR8380 as a reference. I was getting some low ohm readings on the primary and secondary voltage output for video and other circuits - the readings were around 1 to

2 ohms. I tried checking the ohm reading on the HV output side and wasn't getting any shorted out or low ohm reading - and I don't recall much of any reading on higher ohm ranges.

The right side of the screen was developing a wave along it (not straight) just before it died the last time. The TV only lasted for about 15-20 mins before the HOT shorted out again. Now there is a high pitch ticking sound from the TV when the power cord is plugged in.

I'm waiting for a Sams Photofacts to arrive for this - but could use any help / advice about the right side horizontal issue.

Thanks, Glenn

Reply to
Tom Tom
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Replace the Flyback and of course the HOT again !

Sorry, but when a HOT is taken out in that fashion, the flyback is almost all the time the cause along with the low voltage supply sections some circuits use from the flyback.

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Reply to
Jamie

On Sun, 24 Aug 2008 15:58:27 GMT, "Tom Tom" put finger to keyboard and composed:

I'm not familiar with that particular chassis, but have you checked the tuning cap in the horizontal section? Is there a high voltage (2kV) ceramic cap nearby?

- Franc Zabkar

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Reply to
Franc Zabkar

I don't recall seeing anything resembling a tuning capacitor. This chassis seems to have minimal components to it. But I'll look at the schematic and see if one is listed on it. I'm taking a step back right now while I do some more research and thinking on this problem.

Glenn

Reply to
Tom Tom

Thanks for the help. I've been thinking that was going to be my next step. I don't see any markings inside the TV to indicate what the CRT voltage should be set to - I think I saw something in another posting with the same chassis (a 27" TV) that said 27KV. I also need to source a HV probe.

Any suggestions for a good source online for flyback transformers? When I researched I found one priced at $17.95 and another at $39.99. Just not too sure of the quality I would be getting.

Glenn

Reply to
Tom Tom

On Sun, 24 Aug 2008 21:06:16 GMT, "Tom Tom" put finger to keyboard and composed:

A tuning cap is invariably connected across the C-E terminals of the horizontal output transistor. It forms part of the horizontal resonant circuit and has a typical value of the order of a few nanofarads.

This Philips set uses a different chassis, but see the section half way down the page where the author discusses a failure in the tuning cap:

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- Franc Zabkar

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Reply to
Franc Zabkar

the highland electrix site has a long list of common philips faults.

-B

Reply to
b

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