Mulja tv repair portal

Equipment Repairs => LCD TV forum => Topic started by: Turnip on March 27, 2015,11:35:54

Title: Technika LCD22DVDID-208 - Sound buzz at min volume.
Post by: Turnip on March 27, 2015,11:35:54

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.

Title: Re: Technika LCD22DVDID-208 - Sound buzz at min volume.
Post by: jordan on March 27, 2015,12:18:54

Replace main capacitor 120uF/400V in PSU

Title: Re: Technika LCD22DVDID-208 - Sound buzz at min volume.
Post by: Turnip on March 27, 2015,12:27:30

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.

Title: Re: Technika LCD22DVDID-208 - Sound buzz at min volume.
Post by: downunder on March 27, 2015,15:13:18

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

Title: Re: Technika LCD22DVDID-208 - Sound buzz at min volume.
Post by: Turnip on March 28, 2015,10:02:59

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.

Title: Re: Technika LCD22DVDID-208 - Sound buzz at min volume.
Post by: downunder on March 28, 2015,15:17:03

Nice one, Chris. Flash Jordan weaves his magic again.

Yeah, have had various el cheapo Chinese brands with plastic panel backing. Work OK till the CCFLs start to age and generate a lot of rubbish which affects the eeprom stability. Can cause shaky and flickering picture, blacking out, lines on screen, loss of colour and pixilation.

Bruce has a solution for it though.    Bruce

Title: Re: Technika LCD22DVDID-208 - Sound buzz at min volume.
Post by: Turnip on March 29, 2015,12:00:29

Hi Bruce,

Guess it's 'Oil Drum Row', as you seem unusually modest about a profitable solution.

Must admit that replacing tubes in small screen sets isn't the best of fun, as they seem to go 'pfft' when nearly re-assembled, even if it's just an 'end corrosion' jobby - Chris.