Acoustic Solutions 37inch LCD LCD37761F1080P

[paul2463]

Hello
I managed to pick up one of these TV's on Ebay yesterday for a very reasonable sum, it was advertised with a small fault which I am hoping to repair.

The fault is that there is a buzzing from the TV when there is large amount of darkness in the picture it is showing, so if its bright there is no noise, but it reaches a darkness level and then starts buzzing, the buzzing does not increase with the amout of blackness, but when it starts, it stay going until it becomes light again.

The TV works perfectly other than this, I have tried turning the brightness up and it had no effect, in fact i put it on a blue setup picture ( buzzing started) and changed the brighttess levels from full down to full up and the buzzing remained but constant.

any help gratefully recieved 

Paul

[watteau]

Hi
Is this a mechanical buzz, or a buzz on the sound (does 'Mute' stop it)?
There have been problems with the separate audio amplifier panel, (I think
it uses  one in this model), if so, try tightening the panel mounting screws.
Regards

[t1412]

check the connection from the power to the main board for dry joints and the caps next the audio ic

regards
shaun   

[paul2463]

It must be a mechanical buzz as when I mute the sound, well i didnt push mute, I turned the sound down to zero, the buzing continued, I will have a look in the back ( something I am completley new too, never pulled a tv apart before) and check for loose screws and some dry joints

thanks for the quick replies

[paul2463]

Hello and thanks for all the help

I took the back off the TV, turned it on and there was the buzzing ( as it was a dark screen with nothing connected) I traced the buzzing to the speakers ( strange as I had tested them) I muted the sound which had no effect on the buzz at all and it was still coming from the speakers, I traced the speaker cables back to the board ( pictured attached) I unplugged each speaker in turn, with both unplugged all sound stopped, I plugged them back in again ( the buzz was back) and unplugged the cable that went to the yellow connecter at the top left of the picture, all buzzing stopped, I plugged it back in again - NO BUZZING !!!

I removed the board so I could take the picture then rebuilt the TV and everything is hunky dory - thanks for the ideas on what to look for.

[paul2463]

 a small update.....

this morning the buzzing has started getting a bit louder again, so I have ordered another one of those audio amp boards to see if I can cure the problem that way, if that doesnt do it then the problem is elsewhere.

oh well there I was happy for a while....

[downunder]

Hi paul2463,

A thought.....does the power cord have a ferrite bead on it? These have been known to cause buzz in the audio amp. If so, try it with a n ordinary cord.

[paul2463]

al the three cables connected, ( the speaker wires and what I presume is the power lead connected to the yellow connector) all had what Ithough was a black rubber ring that the wires were wound around a couple of times, are they what you mean?

[Turnip]

Hi Paul,

Can't remember if you said if the buzz was independent of volume setting ? might be significant.

Guess it's Vestel where they make much use of plastic covered ferrite beads.

If you need an AMPXXx panel, have heaps as they rarely give trouble - Chris.

[paul2463]

Hi Chris

Yes the buzz is independant of the volume settings, but the buzz is deffintiley coming from the back of the speakers, I have ordered one of the Ampx boards for £2.50 off eBay, if it works it will have brought the whole expenditure to nearly £25.

Regards

Paul

[downunder]

Paul, I was referring to the Mains (AC power) cord that connects to the wall outlet, but ferrite beads on other wiring can also cause the buzz. Also if the display panel has a plastic back cover as opposed to a metal one, it may be picking up garbage from the backlights.

[paul2463]

The mains (AC) lead does not have a ferrite bead on it, I will try it with the new AMP board when it arrives, if the fault persists then I will look elsewhere

thank you for the advice and knowledge of where to look

Regards

Paul

[Turnip]

Hi Paul,

You noted that the buzz 'comes from the back of the speakers' at any or no volume. Seem to recall that the 17PSXXXX power supply can buzz, usually if the Main cap is duff.

Just a thought, as suspect Bruce is into Dream-time stuff, again - Chris.

[downunder]

Nah, Turnip,

Dreamtime is for those who watched the first boat people come to these shores ie the aborigines in Terra Nullis watching a fleet of convicts pulling into Botany Bay.

Suffice to say, Bruce is now a quuq hero.

[Turnip]

Hi Bruce,

Always thought you should be, Even a Blue Background 'Super Hero' as -

Leave you to fill the details as wouldn't want to do anything to dampen any existing Quuq Super Hero's parades, even after a glass or two.

All fun, but as we actually repair as well as having the needy laugh - we should maybe be elevated to perhaps 'Hero * of some class, for folks who actually try mend things, and with a chuckle  - Chris.