LG 47LB5900 led's flash

[nwcs]

I have one I thought was going to be easy. It came in with no backlight. I found several bad LED's so I ordered a complete set of LED's from Shop Jimmy. The only problem is they did not have the original but had a substitute set. I tested the LED's when I got them and they tested good. After installing them and testing the LED's just flash repeatedly ever second or so. Tested the voltages on the power supply and here is what I get:

on P801 LED+ both when first turned on get 30v then creeps down
on P201
Pin 1 PWR-ON 2.7v
Pin 2 drv-on 2.9v
Pin 3 2.3V
pin 4 p-dim1 4.2v
pin 5 2.3V
pin 6 2.7v
pin 7 gnd
pin 8 p-dim1 1.7
pin 9 24v
pin 10 22v
pin 11 gnd
pin 12 gnd
pin 13 9v
pin 14 12v
pin 15 9v
pin 16 nc
pin 17 & 18 gnd
then they drop to ov
I have replaced the power supply and main board with ones I have in stock but I am not sure if they are good. I did try a different set of LED's that are from a different tv and they also blink. Any help would be appreciated.

[budm]

Re: LG 47LB5900 led's flash

https://www.badcaps.net/forum/attach...6&d=1522084652
Based on LED Voltage chart for the 47" screen, the loaded Voltage should be 117VDC AT 230mA.
You have two set of LED strings driven by individual Boost converters so you need to test Voltages of both L+ OUTPUTS by leaving all the probes connected before turning on the TV to see how high the Voltage jumps up to before coming back down due to protection circuits kick in, meter set to 200V scale.
BTW, the power supply board should match your LCD panel size as shown in the Voltage chart.

[nwelec]

Re: LG 47LB5900 led's flash

I did that and 30v is the voltages I get. I get the same issue with original power supply and two I have got from shop jimmy. I wonder If I am getting bad power supply's.

[nwelec]

Re: LG 47LB5900 led's flash

And yes I agree with the power supply size. I replaced with the exact sames P/N power supply.

[budm]

Re: LG 47LB5900 led's flash

What happen if the LED connector not in place? The L+ should jump over 150V without LOAD (LEDs) connected, if not there is problem on that power supply board.
And what DC V do you have between the two legs of C219, C224, main filter cap C610?
http://www.shopjimmy.com/lg-eay63072...-led-board.htm
LG EAY63072001 (LGP474950-14PL2) Power Supply / LED Driver Board
Pictures provided by shopjimmy.

[CapLeaker]

Re: LG 47LB5900 led's flash

What happens if you force the PSU on without the main board?

[nwcs]

Re: LG 47LB5900 led's flash

Sorry I did not know anyone else replied to me. So I unplugged the LED's and the voltage goes to 180v on one LED+ and 140v on the other LED+ pin. I am not sure how to force the psu on.

[nwcs]

Re: LG 47LB5900 led's flash

I do not know what is different but now I get 92v on one led+ and 140v on the other. Am I dealing with bad power supply's? I would like to try and force the psu on with the main removed if some one can explain how to do that.

[dick_barton]

Re: LG 47LB5900 led's flash

The power supply shown in post #5 by Budm indicates the voltages for a 47" set to be 117V. I would suspect the Led+ line showing 140V has an open circuit led(s) or an open circuit somewhere along the wiring or maybe one of the back panel led strip connectors.

[nwcs]

Re: LG 47LB5900 led's flash

These led's are a replacement set because the original ones had too many defective strips. So I would normally agree but I used a know good set of led's with wiring and it too did the same thing. I also went through with my led tester and tested all led's. I may pull the led panel again and check the wiring.

[nwcs]

Re: LG 47LB5900 led's flash

Well I went back and reseated all the connectors to the led strips and now all led's are working. Thanks for all of the help again to all of you.