LG 42LE4500 No display

[thuss]

Re: LG 42LE4500 No display

Hi

Ive just realised that if I shine a bright light on the 42le4500 whilst in a dark room, I can see the image on the screen. So I assume that the back lights are not working.

Has anyone come across this and cured it with a power suppy board change?

[thuss]

Re: LG 42LE4500 No display

Hi

Has anyone repaired a 42le4500 power supply?

[thuss]

Re: LG 42LE4500 No display

ok thanks

[tom66]

Re: LG 42LE4500 No display

Probably means the output above or below it is supposed to be 20V, normally PWR (meaning POWER ON) is >2V for on, <0.5V for off.

[thuss]

Re: LG 42LE4500 No display

Hi

I thought looking at the power supply picture next to pwr on (which is in a box) it states 20V?

[tom66]

Re: LG 42LE4500 No display

Why do you think PWR should be 20V?

[thuss]

Re: LG 42LE4500 No display

Hi

I have the same tv (42LE4500) which does the same thing.

I have checked the power supply with the screen working and I get a reading for the pwr 3.33 and Dvr as 12.

When the screen goes black with the sound still working I get the same readings i. pwr 3.33 and dvr as 12. Should my pwr be 20v? Is my power supply faulty?

Thanks in advance

[tom66]

Re: LG 42LE4500 No display

Try checking diodes, fuses, MOSFETs etc. I don't have enough time to trace a circuit out, so you can only really try the obvious.

[dave bro]

Re: LG 42LE4500 No display

Any idea what circuit to start with or the most likely problem circuit?
Would it help if I tried to post a better picture of the power board?

[tom66]

Re: LG 42LE4500 No display

Schematics are not available, and I can't see the power board clearly. You can try to repair it yourself by tracing circuits out and replacing parts. Or you can replace the board. I don't think either will be better than the other, except a component level repair will be much cheaper.

[dave bro]

Re: LG 42LE4500 No display

Ok, thanks. Is it possible to get a pdf of the service manual for this tv to maybe narrow the fault down?
Also, in your opinion considering the age of the tv, is a replacement a better option or a repair?
Thanks you for your help so far.

[tom66]

Re: LG 42LE4500 No display

The voltages, from the main board, should be both 3.3V, or so, as they are. But the LED backlight is not coming on, so something is wrong with the power board. Due to how these sets work, a single LED failure can't cause the whole panel to fail to light.

[dave bro]

Re: LG 42LE4500 No display

ok, thanks

what shuld the voltages be?
And anywhere I can get a replacement you know? Or is I worth getting replacement. TV is 2 years old?

[tom66]

Re: LG 42LE4500 No display

OK, it seems like the power board is bad.

[dave bro]

Re: LG 42LE4500 No display

Are they right? They are the readings before screen goes black, when screen goes black;
DRV ON is 3.23V and PWR ON is 3.32V

[dave bro]

Re: LG 42LE4500 No display

DRV ON is 3.23V and PWR ON is 3.34V.
Do they seem right? or am I not doing it right?

[tom66]

Re: LG 42LE4500 No display

You need to check the PWR ON and DRV ON signals. Multimeter red probe on appropriate pin, black probe on chassis, 20V DC range.

[dave bro]

Re: LG 42LE4500 No display





I hope these are what you mean?

Also I noticed if I dimmed the picture when it was working it would go black screen straight away? Not sure if that gives any my help. Thanks for you help.

[tom66]

Re: LG 42LE4500 No display

OK, there is a connection cable going between the power supply board and the main video board. Can you see a legend label next to this connector? If so take a photo of it, or list the labels.

[dave bro]

Re: LG 42LE4500 No display

Just checked it and the screen is not glowing