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Validity of Flyback Test?

Some years ago, I built the flyback tester that was described in Sams FAQs - the one with the simple two-transistor oscillator, connected by winding your own 10 turns onto the flyback core. The flyback is of course tested out-of-circuit. Over the years it has been quite accurate, but the results with one recent flyback are rather inconclusive, and I thought maybe you could give me some advice. I don't have the model # of the set handy, but it's a 36" Sony made in 1998. It came in with a blown HOT and switching regulator, so naturally the flyback was the first thing I suspected. Normally when a flyback is tested with this device, it will produce a decent-looking arc of about 1/2". The flyback in question, however, seems to produce a weak arc of less than 1/4", and it doesn't have the "sizzle" and thickness I normally see with this test. Given the size and high voltage requirements of the CRT, I expected a lot more from this flyback (if it's good, that is). Would I be right to suspect it as bad? I really don't want to replace the other components and leave the original flyback installed, because if it's bad, as you know, it will just take out the other components again (nice design, Sony). Any advice would be appreciated.

Reply to
packrat79
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How much is a new flyback? A while back I replaced one on a 32" Sony which was arcing internally, it was surprisingly inexpensive and fixed the problem.

Reply to
James Sweet

"James Sweet" wrote in news:iADvj.13$A93.12@trndny08:

I recently put a new flyback in a 12" TV,it cost less than $20 from Acme Enterprises. My old FB smoked.

--
Jim Yanik
jyanik
at
kua.net
Reply to
Jim Yanik

So chances are it probably is bad huh? That's what I figured. However, Sony has discontinued this part, so a generic replacement will have to do (I could only find one supplier, with one left in stock). I didn't think Sony discontinued parts so soon, but I guess that's the trend these days.

Reply to
packrat79

Hard to say for sure, but if it isn't super expensive it might be worthwhile to just replace it and see what happens. Flybacks can be difficult to test, there's too many characteristics that are critical in some sets. I have a flyback ring tester which works pretty well but even that isn't 100%.

Reply to
James Sweet

I agree. If the self oscillating circuit works as well as it did, a ring test probably won't be any more definitive without a side-by-side compsrison. You may have to try a new one.

You might compare the DC current through the oscillator with the suspect flyback, and with a known good one. If it's really significantly higher, then that would be one more piece of evidence suggesting a bad flyback.

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Reply to
Sam Goldwasser

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CAn you give a URL for the tester you mentioned. I didn't see one on Sam Goldwasser's repair FAQ site.

H. R. (Bob) Hofmann

Reply to
hrhofmann

This is the one I have:

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Reply to
James Sweet

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Thanx!

Reply to
hrhofmann

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