LG 55 UF6450-AU tv no audio,Flickering screen intermittent, not turning on.

[Lisadk]

I have a Lg 55 uf6450-UA tv with no audio, no display, a flickering screen with a red light that blinking 3 times on the display when I power the unit on. This occurs temporarily when the tv has been unplugged for a while. The voltages on the power supply board at this time on p201 connector -pin1-3.3vdc pwr-on, pin 3-0 Grd, pin 5- 13.2,vdc pin 7-13.2vdc
pin 9-0v Gnd, pin 11-3.4vdc. All the readings are steady on the connector.
At the Test point 13.2v a steady 13.2vdcvolts. The voltages at P 801 the Led connector read LED+ 154vdc, LED-23vdc, led+ 319-346vdc not steady, led- 0v. I tested these points with the red positve lead & the black lead grounded to the chassis.
I also checked the voltages on the Main board connector coming from the power supply board Pin 1- 3.3vdc. Pin 5 -13.3vdc. The Led on the Main board(near the orange sticker c2314) is lite while the Tv is powered on.
The audio connector JK3800 no led lite is display.

The flickering stops after turning the tv on and off a few time but the red light still blinks 3 times when turning on the tv. The only voltages that changed when the flickering stops on the power supply connector p201 DRV-ON pin 11- 0vdc and the p 801 connector LED+ 138 vdc, LED- 10vdc, led+ 138 vdc, led- 0vdc.
I disconnected the P801 connector on the power supplyboard to the LEDS. The voltage on the power supply board LED+ 138vdc, LED- 0v, led+ 138vdc, led- 0vdc.

In need of locating a schematic for Lg 55 uf6450-UA tv

I think I have burnt out LEDs which is causing the incorrect voltages at the LED connector. I am not sure if repairing the LEDs will fix this TV since the main board is unavailable. Please help.
Any advice would be greatly appreciated.

[neilc6]

Re: LG 55 UF6450-AU tv no audio,Flickering screen intermittent, not turning on.

Yes it sounds like you have bad backlights. The led controller can detect under and over voltage conditions caused by shorted or open LEDs and shut down the backlight. Was just checking out this exact model since picking up a cracked screen one and it is edge lit. Flickering backlights, backlights flashing on at power up and no backlights are all symptoms of bad backlights.

Edit: Looks like this model has main board issues as well. Make sure main board is sending BL-ON/DRV-ON signal https://www.badcaps.net/forum/showthread.php?t=60814

[budm]

Re: LG 55 UF6450-AU tv no audio,Flickering screen intermittent, not turning on.

"The voltages at P 801 the Led connector read LED+ 154vdc, LED-23vdc, led+ 319-346vdc not steady, led- 0v."
OV reading on that Cathode return line means open circuit in the LED string, or bad linking connector between LED strip, or open wire, etc.

[Lisadk]

Re: LG 55 UF6450-AU tv no audio,Flickering screen intermittent, not turning on.

Thank you for the advice..I will do my research on the led circuit and try to move forward on my repair.

[Lisadk]

Re: LG 55 UF6450-AU tv no audio,Flickering screen intermittent, not turning on.

Replaced both 60 led bottom edge strips.part # 1536 WN6419 5 E 6916L2319A,
1538 WN64195E 6916L2318A. Shopjimmy.
Turned on Tv still flashing no display. Voltages at led connector.+155.6 v, -24.5 v, + 332 v, -3.5 v.
Voltages at power supply connector p201 pin 1 3.36, pin 2 1.74,pin 3 0 Grd, pin4 13.28, pin 5 13.28, pin 6 13.28, pin 7 13.28, pin 8 13.28, pin 9 0 Grd, pin 10 0 Grd, pin 11 13.46, pin 12 1.74.
I think it might be the Mainboard ...Sending it out Mainboard for repair.

[jjanssen7]

Re: LG 55 UF6450-AU tv no audio,Flickering screen intermittent, not turning on.

mainboards are very common with that UF series and that 6450 Model...

[Lisadk]

Re: LG 55 UF6450-AU tv no audio,Flickering screen intermittent, not turning on.

Update : I received the main board back from repair installed it and still the TV flickers on the when I turn it on but now the tv has a display on the screen of LG and displays flickers. The main board now has two red leds lit one on the right side of the board and the other is the audio connector.
I order a power supply board since my power supply board making a buzzing noise sound like its coming from the transformer. Installed it today did not stop the flicking when I tuned it on.
I am not sure what to do next. Please help.

[Lisadk]

Re: LG 55 UF6450-AU tv no audio,Flickering screen intermittent, not turning on.

In search of a schematic LG 55 UF6450-UA

[nomoresonys]

Re: LG 55 UF6450-AU tv no audio,Flickering screen intermittent, not turning on.

Thinking that you still have the issue described in post #3, could be a bad connection in the backlight circuit or bad led/s.

[Lisadk]

Re: LG 55 UF6450-AU tv no audio,Flickering screen intermittent, not turning on.

Posted copy

[Lisadk]

Re: LG 55 UF6450-UA tv no audio,Flickering screen intermittent, not turning on.

Thank you for your response. What connection would you check in the backlight circuit? Do you think a component on the Display board is defective? (Picture attached )
I requested another set of LED strips under the warranty waiting for the parts & hoping that will fix my problem.
Thanks again for your advice.

[nomoresonys]

Re: LG 55 UF6450-AU tv no audio,Flickering screen intermittent, not turning on.

Maybe you did get a bad set, some testing there, lots more videos too, just need to sort thru them: https://www.youtube.com/watch?v=Bf5T2wwtydY