LG 47LN5400 LED TV shows no picture but there is sound

[pchatur]

LG 47LN5400-UA BUSYLHR model turning on, has sound, but shows no picture. Flashlight test reveals menu successfully.

I opened the hood, checked the power supply to main board wiring. I am getting standby voltage of 3.5V, all other voltages in the row are also working fine. Power supply board# LG EAY62810801 (EAX64905501(2.2)).

Next, I looked at the output to LED side, it was measuring up to 83V and 79V respectively.

I checked the LED strips, 3 LED strips were not working out of 6 (No. 2nd, 3rd and 4th from top). So, I replaced all, got replacement through ShopJimmy. After replacement also, the same 3 LED strips are not working, although on testing individually (at 24V) each row is lighting up fine.

I am not sure how to move further to identify what could be wrong. Wanted constructive advice.

[budm]

Re: LG 47LN5400 LED TV shows no picture but there is sound

So do you have LED tester that can test the WHOLE LED string?
We also need to the pictures of the board and the whole backside of the TV showing how all the boards are connected together.

[pchatur]

Re: LG 47LN5400 LED TV shows no picture but there is sound

Yes, I have a DC voltage supply where I can adjust the voltage, it has probes for me to test the circuit. I used 24v for one single string.

[R_J]

Re: LG 47LN5400 LED TV shows no picture but there is sound

When you first turn on the tv, what is the voltage on EL67 and EL68 (thats the - of the led's)
Then check the voltage at EL65 and EL66

[budm]

Re: LG 47LN5400 LED TV shows no picture but there is sound

You need 100V (see Voltage chart as printed on your board)to test the WHOLE LED string. 24V is not going to do it, you have two boost converter circuits and two LED drivers for two LED strings.
https://www.shopjimmy.com/lg-eay6281...upply-unit.htm
You need to leave black probe on the chassis and red probe on those 4 test point (one at a time) as asked by RJ, then turn on the TV and see how high the Voltage jumps up to every time you turn on the TV.

[Andrew F. Ali]

Re: LG 47LN5400 LED TV shows no picture but there is sound

Appears to be the usual common LG backlights failure issue. If it turns out your backlights are faulty, replace ALL the strips and I mean every single one to prevent a repair in the very short term.