LG 65UH5500 Momentary Flash Of BackLights

[Pitoniak]

Re: LG 65UH5500 Momentary Flash Of BackLights

I have the same lg65uh5500 with these symptoms:
Power tv on no lg logo flash and nothing shows with flash lite test.
Power button flashes three times.
Red lite on main bd.
Led test 54.1v on all pins of led driver bd connector.
Power bd has 90v on four pins 12.67 on three pins and 3.3v on stand by pin.
Led driver bd connector to main bd show drive on and stand by .6v next two pins 12.67v.
Removed fail wire to ps bd at connector no change.
On main bd connector Has 12.67 on two middle pins And 3.3v on last pin.
What should I check next?

[Pitoniak]

Re: LG 65UH5500 Momentary Flash Of BackLights

[QUOTE=Pitoniak;937921]I have the same lg65uh5500 with these symptoms:
Power tv on no lg logo flash and nothing shows with flash lite test.
Power button flashes three times.
Red lite on main bd.
Led test 54.1v on all pins of led driver bd connector.
Power bd has 90v on four pins 12.67 on three pins and 3.3v on stand by pin.
Led driver bd connector to main bd show drive on and stand by .6v next two pins 12.67v.
Removed fail wire to ps bd at connector no change.
On main bd connector Has 12.67 on two middle pins And 3.3v on last pin.
What should I check next?

[jjanssen7]

Re: LG 65UH5500 Momentary Flash Of BackLights

see post #49&50

[Pitoniak]

Re: LG 65UH5500 Momentary Flash Of BackLights

Problem was the main board
Was getting no “Drive on “
voltage from the main board to the led driver board.
R&R main board on line for $126.

[Pitoniak]

Re: LG 65UH5500 Momentary Flash Of BackLights

Replaced all leds from shopjimmy, before replacing leds turned tv on with fail wire disconnected and all leds turned on. After replacing all leds I turned tv on with fail wire disconnected and now 4 strips on upper right doesn't turn on. Swapped led positions with known good leds and they won't turn on. Need the check wires to driver bd first. But this is all pointing to another main bd again? Is there anything else I need to do or test?
I was not sure if that main bd I originally replaced was brand new!

[nomoresonys]

Re: LG 65UH5500 Momentary Flash Of BackLights

Did you check that the strips lit up before you installed them?

[Pitoniak]

Re: LG 65UH5500 Momentary Flash Of BackLights

Again I swapped the position in a known good position and they lit up

[Pitoniak]

Re: LG 65UH5500 Momentary Flash Of BackLights

Something is making all of these lg65uh5500 fail the same. I wonder if it is a defect main bd icu chip that lg is using or is something else. We know for fact the leds are crap. That’s way I replaced my leds with shopjimmys improved leds or so they say. Or maybe something on the led driver bd? Scratching head?

[jjanssen7]

Re: LG 65UH5500 Momentary Flash Of BackLights

They are overdriven. There are 6 circuits on your LED driver board. I've had some success lowering the power output at the driver board and turning down the backlights in the service menu. No comebacks on the 5 or 6 I've done like that so far.

[Pitoniak]

Re: LG 65UH5500 Momentary Flash Of BackLights

That’s the first thing I did when I replace the main bd is lower the the back lites . I think that is the main reason why thiese tv fail when new customers don’t turn back lites down.
Question how did you lower the power out put?

[jjanssen7]

Re: LG 65UH5500 Momentary Flash Of BackLights

https://www.badcaps.net/forum/showth...light=65uh5500

See post 18&19 of that thread and adjust for your tV. yours have 6 LED drivers, so you will be removing 6 caps. That thread was for the 50" version of your tv.

[budm]

Re: LG 65UH5500 Momentary Flash Of BackLights

That's the first thing I did when I replace the main bd is lower the the back lites . I think that is the main reason why thiese tv fail when new customers don't turn back lites down.
Question how did you lower the power out put?

Show us good clear straight shots of the whole top and bottom side of the LED driver board.

[Pitoniak]

Re: LG 65UH5500 Momentary Flash Of BackLights

The 7.5vDC for the 13V STBY may be normal in standby mode, since there is no separated standby power supply so they may keep the Voltage low just enough to run the main board, and when PS-ON is present and then the PFC Booster circuit kicks in then the 13V and the 80 will be normal.
That is why I ask OP to see what DC V he has on the main filter cap since the PS-ON is present.

Where is the main cap or what is the uf of the cap you are talking about??

[Pitoniak]

Re: LG 65UH5500 Momentary Flash Of BackLights

Lg65uh5500
What I finally found out about this tv's failure is the led connector to the led power board plug in connection is a bad wire connection to the led power board pins. I removed each wire from the connector and carefully crimped them tighter.
I did replace all leds with a set from shopjimmy previously. I too was getting a group of 4 leds strips not lighting up after replacement. That was caused by the bad connector pins connection. I also decided to do the resistor mod on the led power board and tested about 53.1volts with led tester on each set of pins on the led connector.
FYI…You can power up this tv by disconnecting the fail wire at the power board connector. And then trouble shoot.
Hope this help others in troubleshooting this tv.