LG 42LB5610 BackLight problem.

[HellasTechn1]

Re: LG 42LB5610 BackLight problem.

I re checked the leds one by one with a 3v lithium battery and they appear to work at full brightness. I know for a fact that the leds i replaced are 3V 1W. The model that comes to Greece may be different, or is there an other explanation ?

[Trevtron]

Re: LG 42LB5610 BackLight problem.

Well I had to take an educated guess at the LED voltage, as every one of mine was shorted. Perhaps (a) your model is different to mine (are the output voltages marked on the power board?) or (b) the constant current allows for either.....

[Haydon1]

Re: LG 42LB5610 BackLight problem.

Good day to all !!!

Dear friends, i am now working on this LG 42LB5610 TV. When powered on everything looks normal but about 15 - 30 minutes later the backlight will shut down. Audio can be heared and the panel will display picture. Only the LED's shut down.
After i turn it off and then back on it does the same thing (works for a while etc...)
I am thinking that the led strips are fine since they do work even for 15-30 minutes.

Could you please provide me with guidelines to troubleshoot this problem like for example what measurements i should take ?

Thank you all so much !

i had the same problem,after 3 power boards, pulled the panel apart and there were 3 blown leds, replaced these all is ok now, but got 3 extra power boards.

[Rgyver2]

Re: LG 42LB5610 BackLight problem.

I have an LG TV 42LB6300-UQ that has the exact same power board. My back light was completely bad. 8 strips total, 7 read shorted and one read open - via LED back light tester. i replaced the entire back light ( 32 6v LEDs (4 A strips and 4 B strips, 4 LEDs per strip)). all was fine until back light would still turn off after a few minutes - with new back light. (p-dim related issue)

I found that the back light voltage was stable at 200VDC until the p-dim value went below 0.7vdc. then even when p-dim when back up, the back light would stay off until power cycle.

I found that when the TV was in power saving mode, my p-dim was about 0.79vdc for 80% back light setting. with power save off, 80% yielded 1.9vdc p-dim. with power save off and back light at 45% i had a p-dim of 1.19vdc. all other voltages (3.5, 12, 24, power on 3.4, and dvr-on(boost) 3.4) were as expected.
when the P-dim dropped below 0.7vdc the back light would turn off - back light voltage would drop from 200 to 87 vdc. And i verified i still had 3.4 vdc on the DRV-ON pin (when i had the old, BAD back light connected, when the DRV-ON signal would drop out and the back would drop to 87vdc).

What would i check or repair to make the PWM circuit for the back light stable when it receives a power saving p-dim value like 0.55vdc?

also, I ran the TV with power saver off and back light at 45% for two hours without any issue P-dim at 1.19vdc. Then i started lowering the back light %. When i got to 23%, the back light turned off. P-dim was at 0.67vdc (drv-on was still 3.4vdc). raised back light back to 45% and p-dim was again 1.19vdc. but the back light does not come back on, until power cycle.

any advice or suggestions would be greatly appreciated.

[Rgyver2]

Re: LG 42LB5610 BackLight problem.

I fixed my back light p-dim issue.
i replaced the power board - LG EAY63071901 - (circuit board rev was a 2.0 (same as original) and white label rev was 4.1 (original was 4.2) (first replacement power board i received was older, 1.9 vice 2.0)

with the new power board everything worked fine. eco mode and low back light percentage no longer made the back light turn off. I tested by running the back light down to 10% with a p-dim value of 0.34 vdc and the back light stayed on.

My best guess is that the original power board and the older (first one i order) had the same failing LED driver IC. the first board was ordered off of ebay and just said pulled from a unit with a broken screen. but didnt say it was tested. my guess is that it had been used for quite some time then pulled. Also, this model power board - EAY63071901 - is know to have issues with this driver IC. if i was able to properly solder items that small (i dont have that equipment), i might have tried to change the IC. but also with the board only costing me around $25, it made more sense to replace it.

[nomoresonys]

Re: LG 42LB5610 BackLight problem.

Nice work, maybe you can test those IC's, compare them to your good board you bought?