LG 65UH5500 Dead

[R_J]

Re: LG 65UH5500 Dead

That 817c is a very common opto

[hbdeals]

Re: LG 65UH5500 Dead

Do you think these might work?

[budm]

Re: LG 65UH5500 Dead

You should try shorting the OPTO pins as RJ suggested to find out if you will get the 13V and the 80V or not first

[hbdeals]

Re: LG 65UH5500 Dead

It tics twice as fast with pins 3 and 4 shorted.

80 volts is 44v
13 volts is 7.5v

[R_J]

Re: LG 65UH5500 Dead

Yes those optos would work, but shorting 3&4 should have told the power supply to turn full on.
What is the background on this tv? did it just not turn on one day?
Looking back at that picture in post #22, that looks to me like something shorted the trace near R10 and that is what opened RF1.

[hbdeals]

Re: LG 65UH5500 Dead

Yes those optos would work, but shorting 3&4 should have told the power supply to turn full on.
What is the background on this tv? did it just not turn on one day?

I'll see if I can find out from the guy I got it from. It didn't look like anyone had been in it. Thanks for help. I've learned a lot from y'all.

[R_J]

Re: LG 65UH5500 Dead

Are you still getting 360 volts on the main filter caps? if you are then we know the pfc section is working.
The fact you get some voltage, although low means the circuit driving T1 is working but if the pfc is not working that circuit is only operating with 160v

[hbdeals]

Re: LG 65UH5500 Dead

Voltage across the 3 filter caps is 384 volts now.

[nomoresonys]

Re: LG 65UH5500 Dead

Heat the opto with a hairdryer see if your voltages come up, go ahead and switch out the opto, if for nothing else to eliminate it from possible suspects.

[hbdeals]

Re: LG 65UH5500 Dead

Heat the opto with a hairdryer see if your voltages come up, go ahead and switch out the opto, if for nothing else to eliminate it from possible suspects.

Heated up the opto a bit = no change

Let it sit = no change

Freeze sprayed the opto = no change

[hbdeals]

Re: LG 65UH5500 Dead

What is the background on this tv? did it just not turn on one day?

The guy said that the "outlet" it was plugged into "went out". He said the TV worked after that but remembers the speakers crackling one morning and sounding funny. It quit working soon after. Just no power one day.

He says they had too much stuff plugged into the same outlet as the TV and the house isn't grounded.

[hbdeals]

Re: LG 65UH5500 Dead

I haven't changed the opto out yet.

Q15 is reading .5 ohms across the pictured legs.

I wonder... seems really low.

[hbdeals]

Re: LG 65UH5500 Dead

may be..LOL or yours hair dryer u used before was soldering hot air gun..LOL spare time and replace this boards but be alarm that you will just go back to first point to read 80 13 volts only

my hot air station is made from a contraption that attaches to a common hair dryer. They burn up after a few months, but hair dryers are really cheap at yard sales.

[hbdeals]

Re: LG 65UH5500 Dead

Capacitor C10 was bad. Replaced it. The ticking stopped and the voltages are back up.

Hairdryer killed C10 maybe?

80v Pins cycles from 88v-91v

(fail) pin = -300mv

13.2v Pins cycles from 11v-15v

The LED power board (P5141) also cycles 11v-15v on it's 13.2v pins.

Bridge Rectifier input = 124v / output cycles from 168v-176v

Big caps = 386v

Across C56 =19.2v

Opto Pin 1-2 = 1v / Pin 3-4 = 4.6v

I did not replace the optocoupler since C10 was the (ticking) problem.

Is it normal for the above voltages to cycle or should they be steady?

Should I still replace the optocoupler?

It's back to where it started, dead, no LED power light.

The rabbit hole ride continues...

[hbdeals]

Re: LG 65UH5500 Dead

I replaced the optocoupler. No changes.

There's other pins that have no voltage on the middle board (inverter). PWR-ON P-DIM? and DRV-ON.

Not sure how to check those.

[hbdeals]

Re: LG 65UH5500 Dead

What are those 2 push button switches for?

[nomoresonys]

Re: LG 65UH5500 Dead

Looks like this is spinning in circles, I would isolate the powerboard and force it on, see what's missing and fix what's not working. Most repair manuals say check the standby voltage of powerboard if it's not there it needs fixed first.

[nomoresonys]

Re: LG 65UH5500 Dead

Wonder if your replacement opto is good, we had a thread a while ago where the new optos from ebay china I believe it was, were doa.

[Diah]

Re: LG 65UH5500 Dead

What are those 2 push button switches for?

these are for reset / reload same to LG OLED, after replace C10 you have cycles of volts. over this forum i followed trouble shooting with user over the phone and we do find he had cracked MOFST. at HOT Area. so i doubt the C10 was bad.. as you my have now cracked MOFST or Diode under cooling sink or the U1 self. best way take parts out from board and test them

[hbdeals]

Re: LG 65UH5500 Dead

these are for reset / reload same to LG OLED, after replace C10 you have cycles of volts. over this forum i followed trouble shooting with user over the phone and we do find he had cracked MOFST. at HOT Area. so i doubt the C10 was bad.. as you my have now cracked MOFST or Diode under cooling sink or the U1 self. best way take parts out from board and test them

I had removed and checked all of those parts under the heatsink before. They tested ok on a cheapie LCRT4 checker. I don't know how reliable that is. C10 was shorting out and causing Q15 to read .5 ohms. Both the LCRT4 and ohm meter shows C10 as a dead short. It is a (badcap).

All of the electrolytic caps on the power supply test good in circuit with ESR meter.