Hello,
I have this TV with the burned leds. I ordered the led strip from Ali and install-it. This is hard as there are a TON of screws to put back.
If you look at the leds they are just burned down, despite of the large aluminum heatsink.
The issue is that too much current is put into the leds, even if it's PWM-ed, it always peaks at 230mA.
So I check under that heatsink to see the Led driver, it's some obscure chip, OZ9998HDN that has no datasheet on the manufacturer website ( O2something).
They have a brochure that has a WRONG and very blurry picture for this part number, it does not correspond to the LED outputs on the Toshiba PCB.
I looked at another chip from this manufacturer and found that 4 output configuration, sort of blurry picture.
There is a pin called Iset that has a resistor to ground, 5.3k on my PCB.
I soldered a 1.1 ohm resistor on a led path to test the current. As in the mini oscilloscope picture, it's 230mA. (250mV/1.1ohm = 230mA)
I put then a 10K potentiometer to measure and at around 6.8k current drops below 200mA.
Done, replace the pot with a fixed SMD 6.8k resistor and remove the 1.1ohm one. Now the Leds should run less stressed and last longer.
Imagine they say Leds are generally 10.000hours life rating but they die out burned.
Just changing the LED would not really fix the problem as even at low backlight settings they still get 230 mA thru and it's probably more than they were designed.
Cheers
I have this TV with the burned leds. I ordered the led strip from Ali and install-it. This is hard as there are a TON of screws to put back.
If you look at the leds they are just burned down, despite of the large aluminum heatsink.
The issue is that too much current is put into the leds, even if it's PWM-ed, it always peaks at 230mA.
So I check under that heatsink to see the Led driver, it's some obscure chip, OZ9998HDN that has no datasheet on the manufacturer website ( O2something).
They have a brochure that has a WRONG and very blurry picture for this part number, it does not correspond to the LED outputs on the Toshiba PCB.
I looked at another chip from this manufacturer and found that 4 output configuration, sort of blurry picture.
There is a pin called Iset that has a resistor to ground, 5.3k on my PCB.
I soldered a 1.1 ohm resistor on a led path to test the current. As in the mini oscilloscope picture, it's 230mA. (250mV/1.1ohm = 230mA)
I put then a 10K potentiometer to measure and at around 6.8k current drops below 200mA.
Done, replace the pot with a fixed SMD 6.8k resistor and remove the 1.1ohm one. Now the Leds should run less stressed and last longer.
Imagine they say Leds are generally 10.000hours life rating but they die out burned.
Just changing the LED would not really fix the problem as even at low backlight settings they still get 230 mA thru and it's probably more than they were designed.
Cheers
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