Samsung LE40C630 - can't power up, STBY light still on

[FlyingNinja]

TV Model: Samsung LE40C630 (LE40C630K1W)
Main board: BN94-02747E
Power supply board: BN44-00340A

Main observations:
- Standby diode is enabled and the light is still
- nothing happens when trying to turn tv on
- ecery capacitors on PS board were replaced. I also get second power board - issues are the same.
- bottom of the main board is dirty (see pics)

Cable connecting main board with power board:
- when disconnected, backlight of the screen is turning on
- every pins on PS board has proper voltage
- "Power ON" pin has 0.7V
- when connected, voltage on every pin are jumping between 0.2-0.3V and their proper value.
- when disconnected, those values are still and proper

Cable connecting main board with touch board (IR + touch buttons)
- every pins has proper voltage (around 3.3V)
- while measuring IR pin and pressing buttons on remote controller, voltage is jumping from 3.3V to lower (depends on whitch button i press) - so tv reads remote commands
- the same thing is with touch buttons

So i think power supply board and inverter are good.
If i disconnect t-con board, issues are the same, nothing happened.
Can you please give some advices how to locate invalid parts?

[CapLeaker]

Re: Samsung LE40C630 - can't power up, STBY light still on

Measure the PSon voltage on the PSU while turning the TV on. If there is nothing, you got a mainboard problem. Looks like some corrosion on the back side of the mainboard? Not good.

[FlyingNinja]

Re: Samsung LE40C630 - can't power up, STBY light still on

"Power ON" pin voltage is as looped as other pins while connected to main board. "Power ON" is jumping from 0.1-0.2V to 0.7V and again and again every ~2 seconds. No matter if in the same time i'm pressing buttons on remote controller or touch panel.

I will try to clean this board with some brush and alcohol.

[CapLeaker]

Re: Samsung LE40C630 - can't power up, STBY light still on

there is not enough voltage to turn the PSU on. Clean off the mainboard and inspect for corroded traces / through holes and repair.

[FlyingNinja]

Re: Samsung LE40C630 - can't power up, STBY light still on

I have cleaned the board and it looks much much better. Cant see any broken parts or source of the leaks :/.




Here is video while measuring PowerON pin.
https://www.youtube.com/watch?v=9fQ7teQycug

[CapLeaker]

Re: Samsung LE40C630 - can't power up, STBY light still on

O.k. Disconnect the main board from the PSU. Take two 1k resistors and jump 5v STBY to PSon and the other resistor between STBY and BLon (backlighgt). The PSU should come on and the backlight too. I can't see the pin out on the PSU.

[budm]

Re: Samsung LE40C630 - can't power up, STBY light still on

No need for force on resistor for the BN44-00340, has already has built-in pull-up resistors for the PS-ON and the BL-ON.
So the backlights should come on and stay on as soon as you plug the TV into an AC outlet if the combo power supply-inverter board is good. So far it sounds like you have main board problem.