Logik LOG32LW782 goes to standby after a while.

[Daveatfernie]

After the sucessful repair of the last LG I've pulled out a 32 inch I've had in a cupboard awaiting a look at hoping for a roll.

As in the title if I run the set with the back removed it will run happily all day long (a week) without problems, put the back on and it shuts to standby down after half an hours use. It will power straight back up if i bring it out of standby but the time it stays on for decreases each time until it's unwatchable.

I've tried a heat gun to the rear while the back is off but to no avail reproducing the fault.

I've recapped the PSU board and with a thermal camera seen that there is a Y0504sa that runs at about 70 degrees on the PSU board with the case off and am wondering if this could be the problem.

I'd be grateful if anyone could shed any light on it.

[tom66]

Re: Logik LOG32LW782 goes to standby after a while.

Most likely C877/C878 capacitros top of PSU board near heatsink. Common fault.

[Daveatfernie]

Re: Logik LOG32LW782 goes to standby after a while.

Thanks Tom again, I'll have a look to get some replacements.

[tom66]

Re: Logik LOG32LW782 goes to standby after a while.

Replace with 15nF/1000V.

[Daveatfernie]

Re: Logik LOG32LW782 goes to standby after a while.

Fitted 15nF/1000V but still has the issue. Are there any other likely problems on the power board? I have noticed that it has a high pitch pulsing switch noise (maybe 5-50 Hz pulsing) with the odd little "flitt" noise while it's on. Picture is bright and stable while it remains on. Am I still looking at the power board as the fault?

[tom66]

Re: Logik LOG32LW782 goes to standby after a while.

What is the voltage across the large 450V capacitor?

[Daveatfernie]

Re: Logik LOG32LW782 goes to standby after a while.

I'll be whipping the back off around lunch time and will get the value then.
Thanks Tom.

[Daveatfernie]

Re: Logik LOG32LW782 goes to standby after a while.

Hi,
The DC voltage is about 330V with a 7V AC voltage. How does this sound? The reading isn't particularly stable.

Cheers

David

[Daveatfernie]

Re: Logik LOG32LW782 goes to standby after a while.

Also noticed that the 24V is sat at 22V. Does this seems a bit low?

[tom66]

Re: Logik LOG32LW782 goes to standby after a while.

Those readings indicate the PFC circuit is bad, a common fault. I have never successfully fixed this, though I haven't tried very hard I must admit.

[Daveatfernie]

Re: Logik LOG32LW782 goes to standby after a while.

Which voltage is leading to the PFC fault?
Would this be fixed by a PSU swap?
Thanks again

[tom66]

Re: Logik LOG32LW782 goes to standby after a while.

Yeah, a PSU fault. What I mean by unsuccessful is I haven't tried component level repairs, yet.