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Technika LCD22DVDID-208 - Sound buzz at min volume.

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Turnip:
Hi Folks,

Odd one this - Cust said she had dropped the set on to the bed when it started to buzz from the speakers at minimum volume. Had the thought that the PS doesn't rectify 50hz, so must be the main board.

Got one and it buzzes much as before. Thought then to replace the PS caps, where the buzz is reduced but now seems to depend on picture content - Blank screen - silent, but with picture - buzz.

While ago would have re-earthed the 'Dagging' - Guess can't be duff tubes as they go all the while. Noticed with the new MB the buzz causes sound distortion, where it didn't before.

Any thoughts ? - Chris.

jordan:
Replace main capacitor 120uF/400V in PSU

Turnip:
Hi Jordan,

Could well explain how 50Hz is getting through, even though the secondary voltages were OK, and replacement secondary caps made only a small difference.

Thanks again - Chris.

downunder:

Hi Chris,

You seem to get all the "easy" jobs. Does this TV perchance have a plastic backing on the panel (as opposed to the normal metal cover) ?             

Thinking outside the square as always.                      Bruce

Turnip:
Hi Bruce,

Recall you have a thing about plastic screen backings, but have not yet met the problem.

This one was indeed easy, but was thrown as have never before met a main cap that was totally O/C but looked perfect - The problem then became obvious with loads of 100hz ripple modulating the DC outputs.

At least now got a spare B.LT712C main board for a Sammy screen - Chris.

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