42LN5300 backlight randomly blacks out

[howardc64]

Have sound. tried 2 main boards with same symptom (so likely ruled out main board for sure)

- Whenever backlight goes out, it is always recoverable by disconnect LED from PSU, test with LED tester, reconnect LED to PSU. Turn on TV. Without using LED tester, blacklight remains out.

- When backlight is on and run white image test, shows no burnt out LEDs (see attached, uneven bright spot on the right center isn't really as visible as the pic)

Seems pretty definitive there are weak LED(s) in the array and LED tester's gradual voltage ramp makes it work again for awhile. Thought I ask other's experiences before buying the LEDs. Thanks

[neilc6]

Re: 42LN5300 backlight randomly blacks out

Backlight issues are almost always the LEDs themselves especially LN, LA, LB or LF series. When intermittent, the voltage can fluctuate and trip the protection circuitry. One bad LED you may not be able to see on a white screen. Just replace them all with new and turn down the backlight level on all inputs. Just picked up a 42LN5700 with cracked screen for parts. Owner said he loved the TV and replaced the backlights previously. Curious, I checked his work and he didn't do a full replacement and had 2 strips that were original and one of them had a shorted LED. He also never removed the standoffs so the reflector sheet was floating and causing shadows. https://techhometravel.com/lg-ln-ser...ed-backlights/

[alfatv]

Re: 42LN5300 backlight randomly blacks out

The least hassle is to replace all LED strips.
It could be also bad contact or intermittent LED, that you need to figure it out by yourself.

[howardc64]

Re: 42LN5300 backlight randomly blacks out

Thanks. Will replace LED strips, test, and report back.