Re: LB5550 Backlight blinks
yup, thanks for all the input though. learned a lot here.
Thank you to the guys at HEGE supporting Badcaps [ HEGE ] [ HEGE DEX Chart ]
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Re: LB5550 Backlight blinks
finally got a chance to open the TV all the way to see the LED strips and found many LEDs burnt out. Changing them out now.
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Re: LB5550 Backlight blinks
with the LED connector unplugged, pin 1 and 3 are 0V pin 2 fluctuates between 160 and 170 pin 4 fluctuates between 205 and 215
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Re: LB5550 Backlight blinks
i double checked the readings at the LED pins and they are as i posted before
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Re: LB5550 Backlight blinks
ok i'll double check my readings again. i see the output voltages for LOW and HIGH labeled on my PSU at 145V and 218V. How can i tell what the cathode return is supposed to be?
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Re: LB5550 Backlight blinks
ok so i checked all the pins in reference to ground and there are no shorts on this IC. what should i be looking for next?...
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Re: LB5550 Backlight blinks
these are what you're talking about, correct? i'm gonna pull up data sheets for these and try to learn something...
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Re: LB5550 Backlight blinks
can you point out to me where you see the two LED strings and drivers?
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Re: LB5550 Backlight blinks
tester showed 200v at pin 3,4 and 100v at pin 1,2
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Re: LB5550 Backlight blinks
here's the bottom of the PSU
can you talk me through what exactly you're looking for?...
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Re: LB5550 Backlight blinks
i do have the LED tester from ShopJimmy, i will test them now and also get a pic of the board.
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Re: LB5550 Backlight blinks
i appreciate you posting your thought process, its actually very helpful for me. I will get the panel number as soon as i can. might be tomorrow though.
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Re: LB5550 Backlight blinks
pin 1: 25-30
pin 2: 102-125
pin 3: 102-155
pin 4: 230-260
as best as i could get them...
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Re: LB5550 Backlight blinks
i also tried it with the main board unplugged and the LEDs still blinked.
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Re: LB5550 Backlight blinks
LED connector has voltage fluctuating as stated before,
itsjust 4 pin LED + - + -
main board connector is as follows
GND - 0V GND - 0V
12V - 12V NC - 0V
12V - 12V 12V - 12V
GND - 0V GND - 0V
24V - 24V 24V - 24V
GND - 0V P-DIM2 - 1.2V
3.5V - 3.5V 3.5V - 3.5V
3.5V - 3.5V P-Dim1 - 1.2V
PWR-ON - 3.3V DRV-ON - 3.3V...
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LB5550 Backlight blinks
I have an LG LED tv here that has standby voltage, and upon pressing the power button the LEDs blink on and off every few seconds. Even when the LEDs are off the display can still vaguely be seen. The voltage at the LED connector fluctuates
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