Sanyo CRT-tv. HOT tested bad. Transformer noisy. What next?

Meatman

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Jul 1, 2010, 1:08:49 AM7/1/10

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Sanyo 35" CRT Mod # DS35590.

PROBLEM: No pic or sound, only the steady, high-pitched whine. Not
very loud. Only unplugging the set stops the noise. Power button
ineffective. Used small tube-in-ear stethescope method to find sound -
sound is from transformer nearby, for sure. This is NOT the FBT, it's
the other one. Main power T'former I suppose. HOT tested bad. So i
know I need that. Checked solders. No bulging CAPS. Gut says replace
FB & HOT and run with it. BUT, is transformer noise related? Please
advise. Thx. Kevin.

UPDATE!!! Just swapped out bad HOT for known good one (different
spec's, from a 32" toshiba crt, but a good HOT). Result is that the
high-pitched whine from the T'former turned into a rapid 'tick' or
'click' sound and at relatively the same volume. Probably 30 cycles/
sec. Does this help? Is this transformer a problem with it alone, or
is it brought on by failed HOT and/or FBT. I need to know what else
to check. Don't mind replacing HOT and FBT, but don't wanna miss
anything either. Thx. Kevin.

Chuck

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Jul 1, 2010, 9:11:00 AM7/1/10

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Make sure you replace the electrolytic capacitor off of the horizontal
drive transformer. Chuck

b

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Jul 1, 2010, 10:46:06 AM7/1/10

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I think you're in the right direction, could be the FBT at fault.
At any rate, there is probably something loading down the line output
stage.
check the diodes in the lines of supplies derived from the FBT
secondary.

Have you eliminated the PSU? Check the psu secondary side for shorted
components or open resistors. You need to make sure the B+ line
feeding the line output stage is correct.

As chuck says, check the horizontal drive circuit and especially the
solder joints. Change the cap (often a polyester film type) between c-
e on the HOT or it will probably blow again.

Let us know how you get on!
-B

Meatman

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Jul 4, 2010, 12:51:40 AM7/4/10

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Me, OP: Ok, so I have some work to try to do 8^) Please clarify
right quick: Is the SMPS suspect at this point? Or can it reasonably
be eliminated as a likely problem? Just your best experienced guess.
Thx again. Kevin.

b

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Jul 4, 2010, 5:26:36 PM7/4/10

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the whole point of the tests described above is to eliminate things,
including the smps. Until you check the secondaries, who knows?
-B

Meatman

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Jul 5, 2010, 3:29:18 AM7/5/10

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OP: Ok, I'm merely learning. I know what you mean secondaries, in
principle. But I have to find them first! Seriously, I'll do some
lookin' around and try to find a schematic and see what I can gleen.
I know this isn't a DIY hand-held 6-week course on CRT repair. I'll
let you know. Any last info, guys? Thx, Kevin.

P.S.

Meatman

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Jul 5, 2010, 3:35:07 AM7/5/10

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p.s. R413 - no voltage

b

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Jul 5, 2010, 4:34:09 PM7/5/10

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You need the chassis reference - look on the main pcb. I searched
eserviceinfo for the model number, but nothing there. Having the
schematic would help you trace the lines, for sure!
-B

Meatman

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Jul 8, 2010, 4:20:38 AM7/8/10

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In general, or best recollection for my Sanyo, can you approximate the
typical locale of the numbers I'm looking for on the PCB? Maybe the
basic format in general? I see a few likely candidates.