Re: LG 49LB5550-UY with backlights that flicker on and off
This is a big pain for those selling used boards on ebay. I put it clearly in my listings that backlight failure is common in certain models and to test the backlights before replacing the power supply board. Buyers will say the board is defective and the seller is forced to refund with ebay's money back guarantee.
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Re: LG 49LB5550-UY with backlights that flicker on and off
I'm sorry. I didn't even think to take pictures of the wires.Leave a comment:
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Re: LG 49LB5550-UY with backlights that flicker on and off
Thanks for the follow-up on the repair.
Did you take the pictures of the wires?Leave a comment:
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Re: LG 49LB5550-UY with backlights that flicker on and off
A final update for this thread. (PROBLEM FIXED)
ShopJimmy sent me another PSU/LED Driver board and it also behaved like the original board.
I ordered a Complete TV repair Kit (Main board, PSU/LED Driver board, T-Con) from TV Parts Central. I installed all three boards and tested the LED Driver voltages without the LED strips connected and got the same voltage fluctuations as the original and ShopJimmy PSU/LED Driver boards.
I returned all the boards and both ShopJimmy and TV Parts Central said the boards tested good. I can only assume that the fluctuations without the LED strips connected are normal for this PSU/LED Driver board.
At this point I figured that there could only be one last place to look, seeing that I replaced the backlights, PSU/LED Driver board, Main board, and T-Con.
I took the panel apart and inspected the wires connecting the LED Driver with the LED strips. The wires showed signs of excessive heat where they passed through and contacted the panel. Evidently when the voltages got above 147v on one side and 98v on the other (these are the highest voltages the LED tester would apply to the LED strips) they were shorting causing the LED's to flicker. I insulated each wire where they passed through the panel and the LED's stopped flickering and worked as normal.
The LED Driver voltages with the LED's connected and working were fluctuated from 136v - 138v on one and 88v - 90v on the other.
When I checked the backlights level in the settings, it was at 80 (out of 100).
I dropped the setting down to 30. This is where I began to notice a dimming of the screen brightness.
I appreciate everyone's input!!!!
ThanksLeave a comment:
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Re: LG 49LB5550-UY with backlights that flicker on and off
Just an update.
I replaced the backlights. There were four out on one string and three on the other. I received a replacement PSU/LED Driver Board from ShopJimmy, but it was behaving just like the original. The LED driver voltages were lower, but still fluctuated the same. They are sending me another board.Leave a comment:
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Re: LG 49LB5550-UY with backlights that flicker on and off
Shop Jimmy is out of those and suggested an equivalent, which I ordered.
http://www.shopjimmy.com/lg-6916l-17...-10-strips.htmLeave a comment:
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Re: LG 49LB5550-UY with backlights that flicker on and off
Is your panel model LC490DUE-MGA6?
http://www.shopjimmy.com/lg-6916l-19...-10-strips.htmLeave a comment:
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Re: LG 49LB5550-UY with backlights that flicker on and off
Replace all the strips to be certain. I think replacing the LEDs will solve your problem.Leave a comment:
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Re: LG 49LB5550-UY with backlights that flicker on and off
You have to be a bit careful when using the led tester since it doesn't drive the leds at full current and therefore led's which may break down at a higher current than the tester can provide won't be found. However it is a useful tool to do preliminary testing.Leave a comment:
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Re: LG 49LB5550-UY with backlights that flicker on and off
I got my LED tester in. I LOVE IT!!!!! The LED's work just fine. The tester ran one LED string at 132v and the other at 92v. My guess is that the LED driver voltages are too high and cause the LED's to flicker. The customer decided to just replace the PSB/LED Driver.
Thanks for all the help!!!!Leave a comment:
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Re: LG 49LB5550-UY with backlights that flicker on and off
This is a bad backlights issue is what you have. Of course the troubleshooting advice given by the other experts is actually what is done prior to opening up the Panel.Leave a comment:
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Re: LG 49LB5550-UY with backlights that flicker on and off
Those caps should be replaced. Is the BL-ON signal stedy when the Backlights are flashing? I still suspect bad LED backlight strips.Leave a comment:
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Re: LG 49LB5550-UY with backlights that flicker on and off
The 47uF, 160V should have a maximum ESR of around 0.46 ohms. Your readings are considerably higher.
The 33uF, 200V approximately 1 ohm max
Not certain of what the 33uF 350V would be but I suspect around 2 ohms.
Have you also checked their capacitance and do they match what is on them.Leave a comment:
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Re: LG 49LB5550-UY with backlights that flicker on and off
-------------
Dim 1: 2.739v to 2.78v
Dim 2: 2.4v to 2.78v
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Voltages across capacitors LED's not connected
______High_____Low
C801__178.24v__163.52v
C805__147.37v__136.68v
C224__93.47v___90.15v
C219__93.42v___89.86v
Voltages across capacitors LED's connected
______High_____Low
C801__130.61v__121.55v
C805__145.98v__128.41v
C224__92.76v___90.3v
C219__92.38v___89.7vLeave a comment:
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I picked up this TV that the prior owner said - just died.
Tested the fuse - burnt. A dead capacitor is visible too on the hot side (CP801). Got the replacement power board (cheaply - used). Replaced the board - the TV turned ON!
Now, about a month later (yesterday) I noticed the left side of the screen was flickering from time to time. That was already happening with the antenna input, not through HDMI.
Also, some glitchiness with a Fire stick on HDMI3 - I hit an app with quick dark screen in stick, the TV goes - no input. Then I had to choose the stick... -
Hi everyone I have this TV which was dead one day when I tried to turn it on. I've had the cover off and there was just a pulsating/electrical clicking/ticking noise from the PSU. I disconnected the mainboard as sometimes this works to just fire it up with backlights on? That didn't help. Same noise. Then I disconnected the backlight cable from the PSU and the TV came alive. It appeared to respond to the remote and i'm pretty sure it's fully operational when there is no backlight connected.
However, I am in a dilemma.
I tested the backlight outputs with the lights disconnected... -
Hello,
I am currently troubleshooting an LG 60UH8500 TV (2016 TV). Any help or suggestions would be appreciated.
Overall Issue: When TV is turned on, backlights all come on for about 10 seconds, then all go out. There is sound and there is a picture on the display (obviously hard to see without backlights, but it is there).
What I Have Done So Far: 1) Removed the back TV cover to expose the boards (Power Supply, Tcon, and Main), 2) blew out any dust and cleaned all connections, 3) Noticed that the LED backlights are fed from two separate connectors... -
Need a little help here.
the backlights flicker when watching tv. Everything else works as it should. Also it's not the picture that's flickering just the leds.
I tested the leds and all light up and measure 77.5v volts. I took the tv apart to double check leds and they all work and light up perfectly.
I believe it's the power board causing the issue however I cannot find a replacement board so I'm stuck to finding the bad component. The power board has a sizzling sound coming from the backlight transformer. I replaced that and problem persist.... -
So i ran tests on the power supply and all of the voltages going to the main board are fine. I tested all of the capacitors on the psu with an esr reader and they all pass. All diodes pass also. But when a reading is done on the 4 pin white led connector on the top of the board, the voltages will flicker to 5Vdc for a fraction of a second and go out again. For that fraction, the LED backlights light up. Anyone have any clues to this situation?...
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