LG 42LE730N no backlight issue

[PowerAmpFreak]

LG 42LE730N with no backlight.
I measure across the LED output supply and it reads like 107V on all pins.
Could it be an open led-string inside the panel ?

Please advice

[Andrew F. Ali]

Re: LG 42LE730N no backlight issue

Yes. Testing the backlights may prove an open LED or two.

[PowerAmpFreak]

Re: LG 42LE730N no backlight issue

Yes. Testing the backlights may prove an open LED or two.

What confuses me is, the screen is probably built from several LED-strings and should not result in a complete black screen, more like certain areas of the screen is dark.

Take a look on the above pictures.
The 2 leftmost connectors power the led strings and there are a number of conductors there powering up a set of strings as I take it.

[martino]

Re: LG 42LE730N no backlight issue

it detects a wrong current and or a short. It shuts down for your safety,so your tv don't go up in flames. Still we see tv's that have burned reflector paper and burned led strips sometimes..

[PowerAmpFreak]

Re: LG 42LE730N no backlight issue

It does not shut down nor showing error code or similair by led blinking
It reacts to remote also.
Haven't been able to apply a HDMI source , cause it's hard to change without a screen.

[martino]

Re: LG 42LE730N no backlight issue

kk,then I don't know

[dick_barton]

Re: LG 42LE730N no backlight issue

This looks as though it has a separate led driver board with a pile of mosfets on. Can you post a picture. I'm sure Budm was helping someone out on one of these boards several weeks ago.

[budm]

Re: LG 42LE730N no backlight issue

There are 12 strings of LEDs (you cab see 12 POWER MOSFETs on that LED driver board.
you need to check the Drain pin (big top tab of the MOSFET) DCV of each one of those MOSFETs, you will leave black probe on the chassis, red probe on one of the MOSFET, then turn on the TV and observe the reading, wait a couple seconds to see if the DCV drop down, then turn off the TV and then do the same for the other 11 MOSFETs.

[budm]

Re: LG 42LE730N no backlight issue

BTW, I cannot read the P/N of the power supply board.
EAY????????
EAX????????

[PowerAmpFreak]

Re: LG 42LE730N no backlight issue

Powerboard is EAY 60803101

All 12 powermosfets read 10.85-11.75V constantly

[Fast Alpha]

Re: LG 42LE730N no backlight issue

Reseat cables tightly.