LG 60LB7100-UT backlights turn on then go out .

[cooper trace]

When the set turns on I see the LG logo . Then it goes dark . Flashlight shows no video on the the screen . I also get no command from the remote . Only way to turn off is to unplug it . There is a flashing LEd light on the power board LD701. It blinks 4 times and pauses and 4 more blinks . It will eventually stop and turn off the tv after 5min . 3.5v & 12v & 24v are present . I can't find a service manual on this set . Has anyone seen this problem on this set before ? I have checked the LED's and all of them light up .

[cooper trace]

Re: LG 60LB7100-UT backlights turn on then go out .

Two more pics

[cooper trace]

Re: LG 60LB7100-UT backlights turn on then go out .

Not sure what I'm doing wrong but it wouldn't let me send all three photos at once . I'm sure it's my problem ! :

[dick_barton]

Re: LG 60LB7100-UT backlights turn on then go out .

You just keep adding them as attachments. One at a time works for me.

[budm]

Re: LG 60LB7100-UT backlights turn on then go out .

https://www.badcaps.net/forum/attach...7&d=1468274024

Please report other DCV readings of all the pins not just the 3.5VDC, 12VDC, and 24VDC.

http://www.shopjimmy.com/lg-eay63072...led-board.htm#
LG EAY63072701 Power Supply / LED Board for 60LB7100-UT
Pictures provided by shopjimmy.
You should also upload pictures of the whole backside of the TV showing all the boards.

' Only way to turn off is to unplug it .' This indicate main board problem.
BTW, do the backlights stay on if you disconnect the cable between the main board and the power supply/LED driver board?

[cooper trace]

Re: LG 60LB7100-UT backlights turn on then go out .

SCLK .895 at startup then goes to .085
VSYNC .395 at startup then goes to .010
SIN 3.2
P-DiM1 1.7
P-DIM 3.2
DRY on 3.1
PWR on 3.4
These are the other voltages .

[cooper trace]

Re: LG 60LB7100-UT backlights turn on then go out .

Also an update while getting these voltages the TV is deciding to work now . So I couldn't try disconnecting the digital main cable to the power board to see if the TVs backlights would stay on . I'll let you know if it acts up .

[budm]

Re: LG 60LB7100-UT backlights turn on then go out .

When it stops working again, measure those pins on post #6 again to see what are missing.

[cooper trace]

Re: LG 60LB7100-UT backlights turn on then go out .

Ok tv went back out yesterday . Here are those voltages .
SCLK / .086
Vsync / .011
Sin / 3.19
P-Dim1 / 2.44
P-Dim2 / 1.735
Dry on / 3.128
Pwr on / 3.14
24v , 12v , 3.5v working

Voltages to backlights connector
Led + \ 55.5v
VC1 / 9.96v
Led + \ 55.5
VC2 / 9.05
Led + \ 55.5
VC3 / 11.9
Led + \ 55.5
VC4 / 8.82
Led + \ 55.5
VC5 / 9.3
Led + \ 55.5
VC6 / 9.3

Any ideas ?

[cooper trace]

Re: LG 60LB7100-UT backlights turn on then go out .

Ok so running tv with no picture for almost an hour then turning it off then back on I get a picture back . Here are voltages that are different when it works .
Sin / no picture 3.189v - with a pic .128v
P-Dim2 / no picture 1.735v -with a pic 3.53v

On the led output connector :
Led+'s \ when not working 55.5v when has a pic 72v
VC 1 thru 6 / when not working voltages range from 9v to 11.9 - when has a pic they range from 9v to 18v

So with the changes in the Sin and P-dim2 voltages would that be my digital main is faulty ?

[fixit4me]

Re: LG 60LB7100-UT backlights turn on then go out .

Did you ever find a resolve? I am having similar issues (same model LB607100-UT)

[Sparky177]

Re: LG 60LB7100-UT backlights turn on then go out .

Was wondering if this was resolved have same problem with the same model seems to be common problem with the LG any help would be appreciated.

[kudalski]

Re: LG 60LB7100-UT backlights turn on then go out .

Same here. Ordered and got both power supply and mother board from eBay. Still same problem about 10 seconds and back lights cut off. but image still there.

All lights come on and all look healthy. took the screen apart and confirmed that.

Just to confirm none of the strips is bad.. opened one of the strips circuits; LED back lights all cut off in about 3 seconds in other words problem is not coming from back lights.

Problem has something to do with power supply assembly which contains the back light power and control.

I am suspecting the power supply I received from eBay has the same problem.

any suggestions? thank you

[Odessa]

Re: LG 60LB7100-UT backlights turn on then go out .

Use Shop Jimmy's LED Tester to test the 6 rows one at a time. I had 2 rows where the voltage on the tester was lower than the other 4 rows. This indicates that there are shorted LED's in those rows. On this model the normal voltage appears to be about 60.2 volts on the 4 good rows. Shorted LED's cause a over currant shutdown of the lamps. The green led on the power supply blinks 4 times indicating over currant also according to the blink code chart from LG.

[tvtimmy]

Re: LG 60LB7100-UT backlights turn on then go out .

Green, just like the Hodag.(Wisconsin inside joke, folks)

[Razor5087]

Re: LG 60LB7100-UT backlights turn on then go out .

If I disconnect the Sin, P-Dim2, and P-Dim pins from the main board the picture returns and plays fine, however I have no control over the backlight adjustment in the menu.