I need a little info. All voltage is ok out of ps.but set is dead other than remote turns on and off. Voltage to backlights read 119 volts on each of the two legs out of ps. Question is it possible one led is out thats causing my problem? Set is only 15 months old. I can unplug lights and theres no effect on voltage reading. I suspect both string of lights are out. Am i correct and can they be replaced?
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55 lg model 55uf6450 no backlights
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Re: 55 lg model 55uf6450 no backlights
Led failed.Please Do Not PM My Page Asking For Help Badcaps Is The Place For Advise, Page Linked For Business Reasons Only. Anyone Doing So Will Be Banned Instantly !
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Re: 55 lg model 55uf6450 no backlights
Thanks- I'm giving it a try. I found two strips of 60 led on each strip. I have 119 volts across each strip. That means 2 volts across each led. Is that correct? I thought it took appx 4 volts for each one. Which is right? They look pretty simple to replace. Where I can I buy these or are they available? These leds are rectangle two leds built together. I guess I have a series -parallel combination. Any help would be appreciated. This set is out of warranty.
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Re: 55 lg model 55uf6450 no backlights
How many wires per LED strip?
Vf will be based on how much current flowing through the device.
https://www.maximintegrated.com/en/a...ex.mvp/id/3256
Can we see some pictures of the boards? I doubt that the Vf will be that low.Never stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956
Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999
Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl
Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/
TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809
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Re: 55 lg model 55uf6450 no backlights
I need to see good clear pictures of the board.Never stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956
Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999
Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl
Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/
TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809
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Re: 55 lg model 55uf6450 no backlights
Thanks for the return budm. I think i overlook the very obvius thing i should check first. The voltage to the lights would come up to 119 volts when i turned on set and i thought it was correct not knowing how the lights were wired. The voltage after checking were suppose to be 193 volts which would make the drop across each light appx. 3.2. Which is what it is suppose to be. I ordered power supply panel today. Should work.
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Re: 55 lg model 55uf6450 no backlights
Is this your power supply board?
http://www.shopjimmy.com/lg-eay64009...ver-board.htm#
LG EAY64009301 Power Supply / LED Driver Board
It uses two LED driver circuit, one per each set of LED string.
That 119V in is the input Voltage to the boost converter to boosted up to light up the LEDs.
The reason you do not have the boosted Voltage can be due to:
1) No BL-ON signal to turn on the LEDs driver circuit, should check that.
2) If BL-ON is present: The DCV at the LED+ pin may be working but it jumps to high due to open circuit in one of the LED string, you should leave the Black probe on the chassis and red probe on either one of the LED + PIN then turn on the TV to see how high the Voltage goes up to, then turn the TV OFF and then move the red probe to -LED and then turn the TV to see what DCV you get, then do the same on the other -LED pin.Never stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956
Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999
Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl
Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/
TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809
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Re: 55 lg model 55uf6450 no backlights
Back to you Budm- I installed PS and got same results. Shorted backlights on to 3.2 turn on voltage and lights came on. screen looked like million of colored dots. I had t-con panel on hand changed it and same results. one side of screen looks little different than other side. had good brightness but no sign of video or picture while trying hdmi input. I tried remote but I could not tell when I had it on right input. I'm thinking main panel at this point. Any thoughts you might have I would appreciate it.
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Re: 55 lg model 55uf6450 no backlights
So before you bought the new power supply board, did you check to find out if you do have BL-ON?
BL-ON comes from main board and at this point it looks like the problem is on the main board or something is locking out the main board from sending BL-ON.Never stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956
Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999
Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl
Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/
TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809
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Re: 55 lg model 55uf6450 no backlights
I had already ordered ps so I waited until it came in and tried it first but I did try the old board and it was same as new board. Nothing much left but main board. Set is only 15 months old so I guess its worth trying. I hope I haven't damaged display by removing it first. It really wasn't that much trouble. I just hope I didn't damage any ribbon cables that caused all those color dots on screen. I double checked and they look ok. Thanks for helping. I will keep you posted.
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Re: 55 lg model 55uf6450 no backlights
Please read my post #9. You do have meter to take measurement, correct?Never stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956
Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999
Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl
Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/
TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809
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Re: 55 lg model 55uf6450 no backlights
When measuring the led+ and led- (both sets) when the TV is plugged in but not turned on yet, I get about 62v on both of the LED+ pins (and like 0.20V on each led- pin) when I press the power button, led+ jumps to about 90v right away then rises slowly to 121.8v over perhaps 8 seconds or so. I read 121.8v, 2.0v, 121.9v, and 1.98v across the led pins.
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Re: 55 lg model 55uf6450 no backlights
There is no voltage spike that I can detect with my multimeter on any of the 4 led +/- pins as power is turned on. Also I measured the pin outs to the main board again because I think the 5th pin down should have 13.3v while turned on, right? I measured again carefully and I am definitely NOT getting any voltage on that 5th pin at any time (on or off). Perhaps that's the problem?
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