Sanyo CRT-tv. HOT tested bad. Transformer noisy. What next?
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From: Meatman on 1 Jul 2010 01:08 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.
From: Chuck on 1 Jul 2010 09:11 On Wed, 30 Jun 2010 22:08:49 -0700 (PDT), Meatman <KevinLee33(a)comcast.net> wrote: >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. Make sure you replace the electrolytic capacitor off of the horizontal drive transformer. Chuck
From: b on 1 Jul 2010 10:46 On 1 jul, 07:08, Meatman <KevinLe...(a)comcast.net> wrote: > 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. 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
From: Meatman on 4 Jul 2010 00:51 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.
From: b on 4 Jul 2010 17:26
On 4 jul, 06:51, Meatman <KevinLe...(a)comcast.net> wrote: > 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. the whole point of the tests described above is to eliminate things, including the smps. Until you check the secondaries, who knows? -B |