Technika LCD 40-270 Flickering screen and no audio

[quiggy]

Hello all,

I've found myself with another problem, which I'm unsure of, I have this 40" Technika TV which had a pretty badly flicking screen and no audio.

I bust it open and discovered 5 bulging caps under the smaller metal thing which I assume is a heatsink? I've replaced those and that's cured the flickering, I'm not sure if it's relevant but they were 3 at 470 microfarad - 35v and 2 at 220 microfarad - 35v.

The sound problem wasn't resolved though, I did notice near the transformer, the component which I seem to have worked out to be something called a Barrier Rectifier? Never heard of one until now, but it has a brown mark near it on the board. I figured this might be the issue and replaced it with one of the same value 20A 45V the set powered on but eventually turned itself off.

Could this component cause no sound? I'm assuming that when the caps went, they've taken something else out with it, has anyone encountered this? or have any idea where I should be looking? Thanks.

I've attached pictures.

[tom66]

Re: Technika LCD 40-270 Flickering screen and no audio

Simple checks, if the set has a headphone output or line level output, or an optical audio output, check that.

It uses class D audio amplifier, you can see near "AMP POWER" here, the two inductors.
https://www.badcaps.net/forum/attach...0&d=1422699631

Maybe worth checking AMP_POWER (12V or 24V typical)

[quiggy]

Re: Technika LCD 40-270 Flickering screen and no audio

Hi Tom, Thanks for the reply, I plugged headphones into the TV and sound was coming through them, I unplugged the headphones and I'm now getting sound from the TV set but only from one side. Weird!

Update: The second speaker is trying to play sound, I can hear it going on and off intermittently

[vinceroger69]

Re: Technika LCD 40-270 Flickering screen and no audio

Try a little contact cleaner in the head phone socket (spray a little in the headphone socket hole and put the haedphone plug in and out a few times it may help clean the contacts)

[quiggy]

Re: Technika LCD 40-270 Flickering screen and no audio

It seems that the scart port is abit dodgy, a quick wiggle and the sound works both sides! Would plugging the headphones in and then out resolve the no sound issue? Just seems to easy to me lol

[quiggy]

Re: Technika LCD 40-270 Flickering screen and no audio

Spoke too soon, it wasn't that easy. If I turn it off at the wall, wait a few minutes and turn it back on. No sound again

[tom66]

Re: Technika LCD 40-270 Flickering screen and no audio

You're probably dealing with contamination in the headphone socket. The sockets have contacts in them which will disable speakers when they are engaged. As vince suggests, try cleaning the contacts in the socket, failing that you'll have to replace the jack.

[quiggy]

Re: Technika LCD 40-270 Flickering screen and no audio

I'll give it a whirl, are headphone jacks fairly generic? or are they like everything else and model specific?

[tom66]

Re: Technika LCD 40-270 Flickering screen and no audio

You'd have to check datasheets to find one that matched the right dimensions, they're usually fairly consistent with any given shape on pin outs etc. You could also find a way to disable it if it does not bother you, most people do not use headphone jacks on the back of their TV (I seriously don't understand why manufacturers stick them on there.)

[quiggy]

Re: Technika LCD 40-270 Flickering screen and no audio

Disabling it would be fine, I considered removing it but that wouldn't work would it? checked the settings but nothing in there to disable it.

[tom66]

Re: Technika LCD 40-270 Flickering screen and no audio

Some of the contacts will be switches. You would need to determine this by using a continuity meter, plugging a headphone jack in and out and beeping for shorts (should be shorted when open, I think) - with power off, of course. You should be able to locate the switches fairly easily that way.

[quiggy]

Re: Technika LCD 40-270 Flickering screen and no audio

For the time being it's working, but if it happens again I'll do that. Thanks for the help