LG 42LN5700 No Backlight - Backlights test good

[neilc6]

Have replaced LED backlights 3-4 times on this model. This one the backlights test good with an LED tester. Replaced the power supply board with no improvement. Have standby voltage and TV turns on (front led blinks and goes out) with no backlight and turns off (front led comes back on). Disconnecting power to main cable does not turn on the backlights.

off/on
12V - 0/12.0
24V - 0/24.7
3.5V - 3.55/3.55
PWR_ON - 0/3.4
DRV_ON - 0/0.08
PD1M1 - 0/0
PD1M2 - 0/0

LED+ 0/55.2
LED- 0/0.5
LED+ 0.2/55.0
LED- 0/12.7

Probably wait until I get another TV same model and start board swapping. Suspect main board at this time.

[budm]

Re: LG 42LN5700 No Backlight - Backlights test good

DRV_ON - 0/0.08
PD1M1 - 0/0
PD1M2 - 0/0
You are missing the BL-ON and the Dim control signals from main board.

[Andrew F. Ali]

Re: LG 42LN5700 No Backlight - Backlights test good

You would have to force the PSU on to determine if it is OK and if the Main Bd. is causing your issue. Normally with some of these LGs if it is the backlights the TV would remain on and you would still be able to get Main Bd. functions.

[neilc6]

Re: LG 42LN5700 No Backlight - Backlights test good

Ok, ordered a main board. An HDMI connector fell off the old one anyway. Will update once I get it.

[Andrew F. Ali]

Re: LG 42LN5700 No Backlight - Backlights test good

Great.

[neilc6]

Re: LG 42LN5700 No Backlight - Backlights test good

Got the same model tv in with bad backlightss (logo flashes for a second on power up). Found two bad LEDs inside. After repairing, I swapped the working main board with the original TV and it powers up with backlight. For reference

Off/On

DRV_ON - 0/3.2
PD1M1 - 0/1.1
PD1M2 - 0/1.1