RCA D52W20 yokes, got any?

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testing. Anyway,

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Ummm, as hard as it may be to believe, a dead shorted convergence yoke should not shut it down. Overheat it yes, but not shut it down.

That is because the output circuit uses current feedback. In other words, short the yoke and you do not pull more current, but it puts out less voltage.

Now if that's what you mean, that the convergence in the channel is out, fine. But if it is "shutting down" the whole circuit, look to the output circuit for trouble.

We probably have one. But I need to know if the yokes are interchangable before getting rid of one. I know they are specified but that's because they are all wired to the same plug for convergence. I don't think it is an inherent difference in the yokes.

However, I have not had convergence windings go bad on a PTV yoke in a very long time. I don't even recall ever having one, but I have fixed so many I can't be sure. Regular yoke windings yes, but not the convergence.

For the convergence yoke to shutdown the output by overcurrent, the only possible scenario would be if BOTH the vertical and horizontal windings are shorted to the core/frame, whatever you want to call it. That would mess with the feedback. If that actually happened to me I would scrutinize that yoke for corrosion, signs of coolant, etc., because it is pretty far fetched. A rare occurance indeed.

JURB

On further reflection, and trying a borrowed yoke, I am incorrect. Yoke is not the problem. I think I was reaching. This has been interesting.....

Originally, set came in for bad flyback. Put in, worked fine for say ten minutes, then conv died. Conv p/s chopper was shorted, but found nothing else bad at all. Replaced chopper, seemed to make no difference in the home. Well, now I have chassis in shop, so better testing is available.

Here is what I have discovered -

1 - conv p/s tries to start 3 times, as it showed 3 quick voltage jumps from sec side.

2 - the 18v p/s start command spikes up 3 times, timed with power supply chirp. 12 volts at TP624 is more like 7 volts.

3 - p/s on command from small signal board spikes 3 times, timed with p/s chirp.

I went over conv board, resoldered and checked with meter all drive transistors, resoldered cable connectors on cobv board and p/s. Looked for anything odd on ssb and def board, saw nothing odd. Will continue.....mind you, sound and unconverged picture work fine.

Thanks, Danny

This sounds like the transistor might have come loose from its heatsink and it overheated.

Well, original was well mounted to heat sink, and it had shorted. RCA replacement (from RCA) reads fine, and I do believe power supply is good.

Latest thing I have tried is DL032 diode on defl board. Saw a reference to it on net, being able to cause this. No help there.

Disregard all. Have service book now, continuing.

Danny

Fixed. replaced small signal board. solved all the oddball problems.

Thanks for the assists

Guess I should finish this thread out. Back in mid May, I replaced the small signal board and aligned. Problem fixed.

Danny