Samsung LN65B650X1FXZA keeps clicking on and off

[kevinm34232]

This is the biggest LCD TV I've gotten to work on. When plugged in it immediately starts clicking the relay on and then off, and continues to do this. If I disconnect the main board from the PS board, when plugged in the PS clicks on and stays on, all voltages look good. I tried disconnecting the other boards and individually and it still clicks on and off.

Don't know what to check from here, did not locate a SM either. Any ideas?

[Dgtech]

Re: Samsung LN65B650X1FXZA keeps clicking on and off

Closer pics of the power supply

[kevinm34232]

Re: Samsung LN65B650X1FXZA keeps clicking on and off

Sorry TV is so big it's standing up in the hallway, not much room to work

Like I said tho it stays on when disco'd from the main board.

[budm]

Re: Samsung LN65B650X1FXZA keeps clicking on and off

Do the backlights stay on also when cable is disconnected from the main board? What is the POWER board P/N? BNXX-XXXXX?

[kevinm34232]

Re: Samsung LN65B650X1FXZA keeps clicking on and off

Backlights do not come on at all, however the 24V is present on the PS. PS part is BN44-00317A

[budm]

Re: Samsung LN65B650X1FXZA keeps clicking on and off

OK, so this power supply board has its own pull-up resistor for the PS_ON (the main board was keeping this line LO until you disconnect the wire back to the main board which allows the PS_ON to go HI (you can verify that). The cable still disconnected, you should check the BL_ON (on/off) pin to see if it is HI or LO, also check the DC voltage at the two legs of the main cap to see it has 360~400VDC on its two legs.

[kevinm34232]

Re: Samsung LN65B650X1FXZA keeps clicking on and off

There is 383V at the caps. There is a BLU ON/OFF and that is 0v.

[budm]

Re: Samsung LN65B650X1FXZA keeps clicking on and off

Good, the PFC is working, the 24V SMPS is working. So it can be that the STBY power supply is weak and cannot handle the load or the main board is bad so it is sending puling PS_ON signal instead of steady HI signal. What you can do is to disconnect JUST the PS_ON pin (every thing else still connected) feeding the power supply and see if the TV will turn on right away with backlights on.

[kevinm34232]

Re: Samsung LN65B650X1FXZA keeps clicking on and off

Disconnecting only the PS-ON pin keeps the TV from cycling on and off but still no backlight.

[budm]

Re: Samsung LN65B650X1FXZA keeps clicking on and off

OK, now see if you do have bl_on (on/off) signal feeding the power supply board or not, if not, then the main board is the problem. BTW, the 24V is still present, right?

[kevinm34232]

Re: Samsung LN65B650X1FXZA keeps clicking on and off

No BL_ON signal from main board, and as you suggested the main PS_ON signal is pulsing from 0v to 5v every few seconds.

[budm]

Re: Samsung LN65B650X1FXZA keeps clicking on and off

Time to dig deep into fixing the main board next, you can do voltage regulators test and good visual inspection first. Diagram of the board will help.