Samsung UA65MU6100W - No Backlight

[samsonn]

Hey all,

I've recently acquired a 65" Samsung TV with a broken backlight. The previous owner mention that the backlight would come good intermittently for a few months after the issue first occurred. There is sound and picture if I shine a torch at the screen.

I've cracked it open and measure the following voltages:

Big cap: 335V

PSU-Mainboard connector:
1 Fail Count 3.37V (Does this indicate a failure somewhere?)
2 ANA-DIM 2.1V (Not sure what this is)
3 A13V 12V (Maybe a bit low?)
4 OD On/Off 3.3V (Not sure what OD is)
5 A13V 12V
6 BLU_PWM 1.8V (Looks good?)
7 A13V 12V
8 Power On/Off 3.3V
9 A13V 12.V
10 GND 0v
11 GND 0V
12 GND 0V


PSU-Backlight Connector:
Between 1+ and 1-: ~11V
Between 2+ and 2-: ~11V

The low backlight voltages might indicate an issue with the PSU or the backlight, looking for any advice to narrow it down further before I pull the panel apart to test the backlight LEDs.

[dick_barton]

Re: Samsung UA65MU6100W - No Backlight

Can you measure the voltage on CNL802 Pins 2, 4, 9, 12, 15 & 16.
Probe on pin 2 and chassis and power on and check the peak voltage.
Power off
Repeat for each pin.

The circuit board says
2D Led voltage = 198V @ 500mA
3D Led voltage = 241V @ 1000mA

[samsonn]

Re: Samsung UA65MU6100W - No Backlight

So while I was testing those pins, after around 5 power cycles, the big transform stopped making noise and I wasn't able to measure any voltages on the backlight connector. So I stopped trying to measure the voltage and plugged the back light connector back in, power cycled it again, and it lite up?

I was only able to measure pins 15 and 16 before it started working again, both were zero volts (and they're not connected to anything so not sure what their purpose is).

I'll try and measure the other pins tomorrow if it stops working again.

[dick_barton]

Re: Samsung UA65MU6100W - No Backlight

I don't know what they are either. If it does stop working again check the led connector plug and socket are both in good order with no signs of burning and that the solder joints of the led socket is soldered well on the power supply board.

Edit
I would also check the transformer solder jounts and that all the soldered joints in that area are all good.

[Diah]

Re: Samsung UA65MU6100W - No Backlight

if it happen again. just disconnect the socket between mainboards and power boards to test backlight if they turn on when you plug it in wall. yours previous way was risk and wrong at Samsung TV.