Vestel shuts off randomly

[p10]

Hi friends,

I'm tired of this LCD TV that doesn't stop breaking. This time, I can't troubleshoot this. The TV has a Vestel PSU 17PW22-4 and main board 17MB12-3. The problem is it goes to stand by state randomly, it's a very hard problem to replicate although it seems to happen more often when the TV has been resting without use. Some time I've seen the LED blink several times after shutting down, but not always.

I've checked everything I can think of. I reckon the PSU is good and so they are the inverter board and tubes. If I disconnect the inverter board from the PSU it makes no difference, although obviously there's no backlight. The PSU voltages are OK.

I think the problem is in the main board, maybe in the main chip VCT6953P which gets very hot (+60 ºC), but I think it may be normal. I resoldered most of the PCB down side as part of a previous reparation.

I will attach diagrams of the PSU and main board.

Some idea? Thank you.

[ReeceyBurger123]

Re: Vestel shuts off randomly

The problem is likely the polly cap on the power supply common issue on all Vestel supplies causing intermittent power down. Have you an image of the set please ?

[p10]

Re: Vestel shuts off randomly

The problem is likely the polly cap on the power supply common issue on all Vestel supplies causing intermittent power down. Have you an image of the set please ?

Hello,

I've checked the capacitors marked in the picture, the two ones with the red cross were far out of specification (22uF caps, one 163 nF, other one 194nF), so I'm replacing both and trying to see if I can make the TV fail again.

If you have any other suggestion, please let me know.
Thank you.

[dick_barton]

Re: Vestel shuts off randomly

Those caps are not going to be in the uF's. They are mains filter caps X1 or X2 cannot remember which ones but they are normally several hundrend nanofarads in value. What is printed on their sides.

[p10]

Re: Vestel shuts off randomly

Those caps are not going to be in the uF's. They are mains filter caps X1 or X2 cannot remember which ones but they are normally several hundrend nanofarads in value. What is printed on their sides.

You are right sir, I miss the dot and I feel stupid. It says .22uF. Now the real values aren't that far although I'd still tell they are bad.

Thank you.

[p10]

Re: Vestel shuts off randomly

Hello,

I've been testing the TV for almost 3 days and worked fine. Hope it lasts a long time. Thank you very much for your help.

Regards.

[ReeceyBurger123]

Re: Vestel shuts off randomly

Replace the 47nf 630v cap should sort it. My bad just seen they are the Ac input likely wont be causing the issue, keep us updated.

[dick_barton]

Re: Vestel shuts off randomly

Hello,

I've been testing the TV for almost 3 days and worked fine. Hope it lasts a long time. Thank you very much for your help.

Regards.

So what did you do ?

[p10]

Re: Vestel shuts off randomly

Replace the 47nf 630v cap should sort it. My bad just seen they are the Ac input likely wont be causing the issue, keep us updated.

Hello,

if you mean the blue 47nF cap in the picture with a green tick, I checked it and measured perfectly fine.

So what did you do ?

I replaced the polyester capacitors I mentioned in my previous post because they measured bad and since that it hasn't failed. Although being aware of how tricky this fault is, I'll never be confident, not even having tested it for 3 days.

Regards.