Samsung UE32F4005 doesn't turn on

[dingari]

Hi, I'm troubleshooting a Samsung UE32F4005 TV that doesn't turn on. The TV is supposed to have shut off all of a sudden and can't be brought back on.

I've checked the PSU, and it seems to be working fine. The fuse is not blown, and if I run the PSU by itself, all the voltages on the mainboard connector are present. For reference, the pin-out of the connector is:

1 B13V  PWM_DIM   2
3 B13V  ECO_ON/OFF 4
5 Vamp  BLU_ON/OFF 6
7 Vamp  GND     8
9 GND   GND    10
11 B5V   A5V    12
13 B5V   PS_ON/OFF 14

If I turn the PSU on with the main cable disconnected, the signals are:

PWM_DIM    3.3V
ECO_ON/OFF  0V
BLU_ON/OFF  3V
PS_ON/OFF   3.3V

When the main board is connected, all the signals are low (0V) and there is only the A5V voltage present on the PSU. I presume this is the standby voltage rail. The PS_ON/OFF signal doesn't change when I press the ON button.

If I unplug all the signals (PS, ECO, BLU, PWM_DIM) the backlight comes on, but no picture.

I've checked the button board, and it seems to be functioning. The KEY1 pin is pulled up to 2.5V, and goes down to 0V when I press the button.

At this point I'm quite certain that there is something wrong with the mainboard. I don't really think it's worth it to get a new board. Is there anything I'm missing? I might take a better look at the mainboard and see if there is anything obvious. Does anyone have experience with this board? From where is the PS_ON/OFF signal asserted? The main processor, or a seperate microcontroller?

Please see attachments for pictures of the two boards.

[dskall]

Re: Samsung UE32F4005 doesn't turn on

Main boards are hard to troubleshoot without schematics. Even with being multilayered. Usually it is limited to checking your mainboard voltages and caps. Trying a reflow

[attainteddragon]

Re: Samsung UE32F4005 doesn't turn on

also check your voltage regulators. i can see 3 on the top side and could possibly be some on the under side too.