LG 65UH5500 Dead

[Diah]

Re: LG 65UH5500 Dead

did you take a look on the down side of the power board..?? you need inspect it... it may there toasted components. the over load you have not normal regards yours statements

[hbdeals]

Re: LG 65UH5500 Dead

There's one tiny spec, like scratch. Everything else looks good to me.

I put 3.3 volts to the STB pin. No change in voltages. 45v and 8v.

Tried 3.7 volts on STB pin. No change either.

[hbdeals]

Re: LG 65UH5500 Dead

That last picture was sort of blurry. Better shot.

[hbdeals]

Re: LG 65UH5500 Dead

The thing that puzzles me is that it was getting the full 80 and 13 volts when I first checked it. 80 and 13 voltages dropped to 45 and 8 after slightly warming the board with a hair dryer. I fully expected the voltages to come back up after the board cooled to room temperature.

A slight temperature change did something.

STB has been Zero volts from the start and still is.

[R_J]

Re: LG 65UH5500 Dead

STB will never have any voltage on it. It is the PS-ON pin for the power supply. If we only knew what that U1 ic was....
What are you heating that changes the voltage?

[hbdeals]

Re: LG 65UH5500 Dead

STB will never have any voltage on it. It is the PS-ON pin for the power supply. If we only knew what that U1 ic was....
What are you heating that changes the voltage?

I hovered a hair dryer over the whole board for 20 or 30 seconds.

[R_J]

Re: LG 65UH5500 Dead

Do you have any voltage on the FAIL pin, and does it change when the voltage drops?

[hbdeals]

Re: LG 65UH5500 Dead

Do you have any voltage on the FAIL pin, and does it change when the voltage drops?

The FAIL pin has 3.4 volts.

I'm pretty sure that pin was Zero volts before because I checked all of the pins searching 3.3 volts several times. Should I jumper the FAIL pin to STB?

[R_J]

Re: LG 65UH5500 Dead

NO. When you push the power button, the main board should change the status of the STB pin, if its not you might have a main board problem
I don't know where the fail line goes, it could be from the led driver board or the main. I also don't know if 3.4 volts on the fail line indicates a failure or if that pin goes low when there is a failure. I suspect it is coming from the led driver board and turns off the power supply if there is a backlight failure.

I would suspect the main board is at fault, you should get the front led to turn on or flash an error

[hbdeals]

Re: LG 65UH5500 Dead

I just checked it again.

The FAIL pin is Zero volts when connected to the LED/Mainboard.

I just noticed the FAIL pin reads -3.3 volts (negative) instead of +3.3 volts when disconnected.

[R_J]

Re: LG 65UH5500 Dead

Thats possible, it comes from D26? likely its anode. without a schematic its a guess.
Like I said earlier, similar power supplies will operate at a reduced voltage in standby to save energy. The main board will operate off the 8 volts in standby mode. so it should show some signs of live. If its not sending the power on command the tv will never turn on.

[budm]

Re: LG 65UH5500 Dead

Post #1: "360 volts on the 3 long capacitors."
It still does not make any sense to me to have that much Voltage on the main cap if PS-ON is not present. Measurement error?

[hbdeals]

Re: LG 65UH5500 Dead

Those caps are measuring 340 - 357 volts. It jumps to 357 with every "tic" sound. It's not a relay click sound, but a voltage tic sound.

[R_J]

Re: LG 65UH5500 Dead

What is the NUMBER on U1 ?????

[hbdeals]

Re: LG 65UH5500 Dead

What is the NUMBER on U1 ?????

I can't find a U1. I will keep looking for it.

[nomoresonys]

Re: LG 65UH5500 Dead

U1 is the big black chip about in the middle of your board in pic. in post #23.

[hbdeals]

Re: LG 65UH5500 Dead

TEA 17 16 T

CKY710

CKX530

D16198?

It's kind of faint and hard to see. lol

https://cdn.badcaps-static.com/pdfs/...f06b063bd3.pdf

[Diah]

Re: LG 65UH5500 Dead

The thing that puzzles me is that it was getting the full 80 and 13 volts when I first checked it. 80 and 13 voltages dropped to 45 and 8 after slightly warming the board with a hair dryer. I fully expected the voltages to come back up after the board cooled to room temperature.

A slight temperature change did something.

STB has been Zero volts from the start and still is.

on your post 12 you replaced R as you test it open. if its was open then you will never had the 80 & 13V at your first measure.. one of tow things the R was not open. or you replaced it with wrong value... this only the things you do it till now and lost the 80 volts.. go back to this point... heating with hair dryer will never accuse this fault.

[hbdeals]

Re: LG 65UH5500 Dead

on your post 12 you replaced R as you test it open. if its was open then you will never had the 80 & 13V at your first measure.. one of tow things the R was not open. or you replaced it with wrong value... this only the things you do it till now and lost the 80 volts.. go back to this point... heating with hair dryer will never accuse this fault.

I just checked the old fuse again. It's still open. The new fuse on the board is still holding up at 1 ohm.

Whatever blew out the resistor is not blowing out the new one.

I guess whatever blew the resistor also blew out something else, maybe U1?

[hbdeals]

Re: LG 65UH5500 Dead

I just tried some freeze spray on U1.

There is no voltage on the 80v and 13 v pins while it's cold.

I watched the meter slowly creep up over a period of 5 minutes as the chip thawed.

The tic sound got louder as the voltage crept back up to 45v.