lg-55UH6090-UF DEAD NO STANBY LGHT

[Super360]

Hey everyone I have a set here that shows 0 signs of life no light no backlight nothing. I checked the psu and its outputting 3.5v and the leds are working fine as well tested with led tester. Main psu fuse is good as well so I'm starting to think it may be the mainboard actually but I'm not sure can you guys help me out here?

[diif]

Re: lg-55UH6090-UF DEAD NO STANBY LGHT

Measure all the voltages at the connector, there is a legend giving their description.

[Super360]

Re: lg-55UH6090-UF DEAD NO STANBY LGHT

Yes all the voltages are fine on the psu standby is like 3.5v and when the led cord is unplugged it gets 177 v when I plug the connector back in the led voltage is back to 0.

[Super360]

Re: lg-55UH6090-UF DEAD NO STANBY LGHT

Now it seems to be getting 8v out of the 3.3v line? I'm a little confused at the moment. why would it be getting 8 v when it should be 3.3? Tell me I'm not crazy I hope the board readout is 3.3 but now it looks like 13.2?

[Super360]

Re: lg-55UH6090-UF DEAD NO STANBY LGHT

Ok so then it's a bad psu boys, looks like im gonna buy a replacement power board on E-bay and will update you guys. Its only outputting like 8v on the 13.2v line so diagnosis bad psu.

[dskall]

Re: lg-55UH6090-UF DEAD NO STANBY LGHT

Was this with main connected or disconnected?

[neilc6]

Re: lg-55UH6090-UF DEAD NO STANBY LGHT

Standby voltage could be 8V and boosted to 13V with PWR-ON logic signal. This is how some Samsung power supply boards work. I would look closely at the silkscreen before determining the PS is at fault. UH series also have high rates of backlight failure though you typically will get a flash of the backlights and the the TV will turn on. A LED tester may not pick up failed LEDs in this model. I would confirm that the TV is attempting to turn on with the PWR-ON signal going high.

[Super360]

Re: lg-55UH6090-UF DEAD NO STANBY LGHT

Mainboard disconnected 8volts boys. How do I test for the psw_on signal? I don't even get the red standby light on the tv like the motherboard is getting power.

[neilc6]

Re: lg-55UH6090-UF DEAD NO STANBY LGHT

The front LED is controlled by the main board so no front LED is not an indication of no standby voltage.

[dskall]

Re: lg-55UH6090-UF DEAD NO STANBY LGHT

With main connected you should get a change in voltage at psw_on when you push the power button.

[Super360]

Re: lg-55UH6090-UF DEAD NO STANBY LGHT

So its 0.0 with it unplugged the mainboard and 0.0 with the mainboard power connected as well no difference as well as pushing power button made no difference.

[neilc6]

Re: lg-55UH6090-UF DEAD NO STANBY LGHT

8V is likely enough voltage for the main board to be in standby mode. If it doesn't turn on, the main board is suspect. If you would like to test the power supply board to see if it outputs 13V, you need to simulate the PWR-ON signal from the main board with >2.5V signal. You can use a power supply or 2 AA batteries plus a 10K or 100K resistor in series.

[Super360]

Re: lg-55UH6090-UF DEAD NO STANBY LGHT

So If I soldered a 100k resistor from pwr_on to ground and then should trip the psu on then?

[dskall]

Re: lg-55UH6090-UF DEAD NO STANBY LGHT

Pwr_on is 0v. So you need to supply it with around 3v

[Super360]

Re: lg-55UH6090-UF DEAD NO STANBY LGHT

Ok well new update. I tried just unplugging the led strip connector from psu and leaving the mainboard pwr cable connected and it actually has a red light in the optical audio port and on the standby. So the answer is obvious now it's the led backlight then.

[Super360]

Re: lg-55UH6090-UF DEAD NO STANBY LGHT

Here's The issue I have the led panel # in the pictures can you guys tell me what number will get me a new led strip on ebay instead of taking the panel apart first?

[diif]

Re: lg-55UH6090-UF DEAD NO STANBY LGHT

Here's The issue I have the led panel # in the pictures can you guys tell me what number will get me a new led strip on ebay instead of taking the panel apart first?

Sticking the model number of the TV into ebay or Aliexpress will show you that there are two strips.

[Super360]

Re: lg-55UH6090-UF DEAD NO STANBY LGHT

I bought some led strips 6916L-2318A so I will give you guys an update when those arrive.

[Super360]

Re: lg-55UH6090-UF DEAD NO STANBY LGHT

Update new leds fixed my tv thank you guys.

[Prestonsback]

Re: lg-55UH6090-UF DEAD NO STANBY LGHT

Same TV with same issue. I unplugged the led strip like mentioned above and the red light on the board lit up but the standby light was blinking. Then I tried to plug the led back in and it went back to no life at all. Not sure if that's what was experienced in this post or not. The psu has been replaced on it. When it first stopped working a video was on the screen and loud pop which sounded like it was from the bottom of the tv came out along with a electronic smell and it went dead. No caps look busted so just trying to make sure it's a led problem.