LG 42LD750 - only Lg logo thengoes black

[domix]

Re: LG 42LD750 - only Lg logo thengoes black

is this okej? what else i must to check or to measure to find a problem why not working
thank for help

[paulstef]

Re: LG 42LD750 - only Lg logo thengoes black

At least they are equal, i.e. they are probably not faulty.

You will need to do a deeper analysis of the backlight circuit. For that you will probably need an oscilloscope. Do you have one?

I would start trying to identify the backlight inverter controller chip, look up its' datasheet and walk my way through the circuit beginning with the typical application schematic usually contained in these datasheets.

[Mikeyboy2007]

Re: LG 42LD750 - only Lg logo thengoes black

I had this tv before, same power board and same problem, the LG logo was coming up then backlights where shutting off.

[domix]

Re: LG 42LD750 - only Lg logo thengoes black

no, i dont have it. so then cant do anything :/

@Mikeyboy2007, do you find the solution?

[Mikeyboy2007]

Re: LG 42LD750 - only Lg logo thengoes black

i ended up just replacing PSU., i now have another one with no power issue so i am going to try and use parts from both to get one working.. try the other forum members suggestions before spending money on a new board, i only purchased a new board as that is what the guy i was helping wanted me to do.

[domix]

Re: LG 42LD750 - only Lg logo thengoes black

okey, than can i close it and wait on ebay or some else, if someone sell broken tv with working psu, i look around and its around 100$, it's to much

[alikate36]

Re: LG 42LD750 - only Lg logo thengoes black

hello I have a similar problem, but I have nothing burned nor any swollen capacitor my lg tv 42LD750 not turn on, the red LED starts to flash but will not start, fuses are correct.
possible solution?

thank you very much

[alikate36]

Re: LG 42LD750 - only Lg logo thengoes black

hello I have a similar problem, but I have nothing burned nor any swollen capacitor my lg tv 42LD750 not turn on, the red LED starts to flash but will not start, fuses are correct.
possible solution?

thank you very much

solved! I was measuring voltage and note that had two pieces of the same reference q gave me a different extent, they gave good 24 v. which failed think 13 I've changed already on the first part q failed was this: BC 003 017 Everlight and replacement q have given me in the electronics store is: optocoupler PC817 the changed part is to arrow and is the twin of the circle.
but my English (google translator ...)

[alikate36]

Re: LG 42LD750 - only Lg logo thengoes black

sorry photo

[Adriatic]

Re: LG 42LD750 - only Lg logo thengoes black

[Adriatic]

Re: LG 42LD750 - only Lg logo thengoes black

Hello.
First thank you for accepting me on this forum.

If someone can help me. I have the exact same tv. The previous owner (thru repair shop) did try to repair the PSU but failed. I got this tv for 40$ and now I'm trying to repair it myself. I'm a hobby / learning type.
However to the point. On the picture attached there is something missing (thought by the color it is a thermistor but not sure). Because of lacking schematics of this PSU board I'm almost blind and I can only guess.
If somebody can help me and check the type of missing element. I would be very

Have a nice day to all of you.

[dick_barton]

Re: LG 42LD750 - only Lg logo thengoes black

Previous post also attached to

https://www.badcaps.net/forum/showthread.php?t=43901