Samsung UN46D8000 dead - No led/backlight

[felipevieira]

Hi!

I have my TV since 2012. Today it is not turning on. No led, no backlight, nothing.

I opened searching for blown fuse, but it is ok.

If I try measures voltage in CN201 with the P28 cable connected in the main board I got all pins with 0V but the 4th pin is 5.32V. But if I disconect the P28 cable, the backlight comes on and I got the following measures in P28 Cable:

Pin 1 - 5.30V (B5V_PW)
Pin 2 - 3.33V (SW_POWER_OUT)
Pin 3 - 5.32V (B5V_PW)
Pin 4 - 5.32V (A5V_PW)
Pin 5 - 0V (GND)
Pin 6 - 0V (GND)
Pin 7 - 12.77V (B18VS_PW)
Pin 8 - 0V (GND)
Pin 9 - 12.77V (B18VS_PW)
Pin 10 - 4.67V (SW_INVERTER)
Pin 11 - 12.77V (B13V_PW)
Pin 12 - 12.77V (B13V_PW)
Pin 13 - 12.77V (B13V_PW)
Pin 14 - 3.03V (PWM1_DIM_OUT)
Pin 15 - 0V (GND)
Pin 16 - 3.02V (PWM2_DIM_OUT)
Pin 17 - 5.02V (OVD_ON_OFF)
Pin 18 - 3.03V (PWM3_DIM_OUT)
Pin 19 - 5.20V (OVD_LEVEL)
Pin 20 - 3.02V (PWM4_DIM_OUT)

If I follow the chart from Service Manual, I need to replace the main board. But I need a second opinion if it is possible.

Link to Service Manual

Warning: The image is in high resolution (~3.5MB each).

Thank you for the help!

[budm]

Re: Samsung UN46D8000 dead - No led/backlight

It is correct that when you remove the cables between the power supply board and the main board you do get backlights then it means the main board is the problem.
When you connect the cable back in, check pin 2, if it is <1V then the main board is not sending the PS-ON signal.

[felipevieira]

Re: Samsung UN46D8000 dead - No led/backlight

Thank you for the reply.

Hummm I think the best way is change the Main board.

Do you know if it is normal this values in PINs 7 and 9?

Pin 7 - 12.77V (B18VS_PW)
Pin 9 - 12.77V (B18VS_PW)

Or they change to 18V when it is necessary?

Thank you!

[budm]

Re: Samsung UN46D8000 dead - No led/backlight

The B18VS may not be tightly regulated power supply, cannot tell until I can see the diagram.
IT may be the same as this label: 13/18VS
https://www.badcaps.net/forum/showpo...4&postcount=10