Technika lcd42-207 humming, buzzing sound

[london-freddie]

Hi all again
Been given this tv to play with, its was going in skip
TV all seems to work fine but has a humming sound coming from speakers, if sound is high it is not that noticeable but when the sound is low its there and it is annoying
Took back cover off expecting to see some bulged leaky caps but everything looks fine, therefore with my limited knowledge I would not have any idea where to look next, any ideas please where to start looking, Power board is a 17PW16-2
will post pics as soon as they upload from my camera to pc

[london-freddie]

Re: Technika lcd42-207 humming, buzzing sound

here are pics

[diif]

Re: Technika lcd42-207 humming, buzzing sound

They might not be bulging or leaking but as it's a Vestel I'd suspect some of those caps are the culprit.
I fixed a smaller Vestel recently with a hum from the speakers by replacing a few of the caps. Check the 3 green ones (IIRC 1000uf) with an ESR tester and the 2 at the top of the mainboard.

[Techstar]

Re: Technika lcd42-207 humming, buzzing sound

Can't wait to hear from the experts on this one mate.

[ReeceyBurger123]

Re: Technika lcd42-207 humming, buzzing sound

Test caps for esr on the mb, also the inverters Ive had cause a slight buzzing when the caps on it fail.

[dick_barton]

Re: Technika lcd42-207 humming, buzzing sound

First, is the hum on the speakers from all inputs tried.
Can you hear it on the headphone out.
Do you have access to an oscilloscope to look at the input /output of the audio IC

[london-freddie]

Re: Technika lcd42-207 humming, buzzing sound

hi thanks for the help
humming seems to be on all inputs not tried headphone jack out
have just changed the 3 X green 1000 16v caps on power board, humming is still there
have not got the mainboard 1000 X 35v caps here to try them, will try and get some tomorrow

[CapLeaker]

Re: Technika lcd42-207 humming, buzzing sound

Look hard at capacitors next to a heat sink. Caps can look fine on the outside, but still be bad, specifically the little ones. You need an ESR meter.

[dick_barton]

Re: Technika lcd42-207 humming, buzzing sound

If my memory is correct I think someone had a similar problem on another thread in this forum where they cured the fault after resoldered all the pins on the audio chip.

[london-freddie]

Re: Technika lcd42-207 humming, buzzing sound

ok just done a naughty one, I have taken some 1000 35v caps off a scrap board and changed the 3 mainboard caps, just fired it up with no inputs connected yet and noise seems to have gone, it was noisy before with no inputs connected, will get it all back together and try it again

[london-freddie]

Re: Technika lcd42-207 humming, buzzing sound

ok all back together humming buzzing gone so looks like it was those mainboard caps, even though i have put on used caps, should probably replace them with new but think will leave these while its ok

[Techstar]

Re: Technika lcd42-207 humming, buzzing sound

Nice one. One to remember that fault.