Samsung UN60D6000 LED Backlight flashing

[ljintexas]

Previous owner told of unit not starting screen just dimly flashing..When I first fired it up..it started and ran just fine..turned off and on a dozen times and fired every time. So I left it running for an hour or two to see if maybe I could reproduce the failure. after about 90 min, sure enough. Dim backlight flash like it's trying to fire but not completing the power up.. Let sit overnite and opened it up this morning..Backlight is coming on for a fraction of a second then going off..cycling over and over. Producing a clicking sound from power supply board. When I powered set down, clicking continued for four more cycles, each one further apart than the previous..I have not found alot of failure history on this model set...I welcome any sugestions.

[stj]

Re: Samsung UN60D6000 LED Backlight flashing

lots of missing screws on the psu,
they may be needed to connect the earth's together.

[ljintexas]

Re: Samsung UN60D6000 LED Backlight flashing

I thought the same thing..in the service manual it shows only the mounting screws that I found installed. Weird. I have found many instances of this issue..There is even a repair kit for the SMPS to address the symptom I am experiencing.

[budm]

Re: Samsung UN60D6000 LED Backlight flashing

If you can make the TV to come on again you should go to the on screen user menu and then turn down to backlights level as low as possible to see if the backlights will stay on and without flickering.

[ljintexas]

Re: Samsung UN60D6000 LED Backlight flashing

If the 5V for PS_ON is causing the smps to cycle on momentarily then off.. then the main board is the issue..Main Board Pin 10 CN201 is oscillating 5.3V on and off.

[ljintexas]

Re: Samsung UN60D6000 LED Backlight flashing

SMPS is generating all the proper voltages.

[dick_barton]

Re: Samsung UN60D6000 LED Backlight flashing

What voltage do you have driving the leds. The board says 333V @170mA

[ReeceyBurger123]

Re: Samsung UN60D6000 LED Backlight flashing

Probably a failed Led tripping the driver tbh. Does the Led drive voltage start off fine then collapse ?

[ljintexas]

Re: Samsung UN60D6000 LED Backlight flashing

One of the LED driver plugs shows just over 400 volts the other shows 335.

[ljintexas]

Re: Samsung UN60D6000 LED Backlight flashing

When I remove pin 2 and pin 10 from cn201 on main board then read the respective pins on the board, pin 2 is oscillating 3.3 volts on and off, pin 10 is doing the same with the same rhythm at 5 volts. With them disconnected, the power supply board still tries to power on and does the momentary LED fire thing. when it did fire up in the beginning, the picture was uniform and bright. No dark areas or spots.

[ljintexas]

Re: Samsung UN60D6000 LED Backlight flashing

Going back to remeasure voltages to LEDs..also will try unplugging LEDs to see if condition persists with clicking on and off.

[ljintexas]

Re: Samsung UN60D6000 LED Backlight flashing

Yes Reecey is does..but it does it with the LEDs totally disconnected too. The PS board continues to cycle a relay every few seconds with LEDs totally disconnected from the board. I noticed that the POWER ON/OFF pin that was 3.3 volts on and off is now 2.1 volts on and off now that the PS board is connected again. The BLU_ON/OFF pin is still 5.3 volts with PS connected.
The only time the PS board does not rythmically cycle a realy and power to the LEDs is when the Main board is disconnected. When I disconnected the BLU_On/Off and POWER On/Off wires from main board connector, no change in PS board behavior..still cycling relay..SMH

[ljintexas]

Re: Samsung UN60D6000 LED Backlight flashing

I am also getting 333 volts momentarily on two sets of pins in each connector with LEDs disconnected. Other two sets of pins are measuring 420+ on one and 160+ on the other.

[dick_barton]

Re: Samsung UN60D6000 LED Backlight flashing

Normally if the voltages are not balanced on the led supplies then it generally indicates faulty led's on that string.

[ljintexas]

Re: Samsung UN60D6000 LED Backlight flashing

They are that way with no LEDs hooked up. i.e. no load on the supplies.

[ljintexas]

Re: Samsung UN60D6000 LED Backlight flashing

Is it possible that the main is not seeing something(a voltage) it needs to see in time so it's shutting the SMPS back down? Strange as with pins 2 and 10 disconnected, the main is pulsing the BLU_ON/OFF and the POWER ON OFF voltages on the board. But with them disconnected, the smps continues to pulse/cycle the relay I can hear.

[dick_barton]

Re: Samsung UN60D6000 LED Backlight flashing

They are that way with no LEDs hooked up. i.e. no load on the supplies.

OK I misunderstood.
But the supplies are not balanced and it looks like you have two identical circuits running two arrays of leds.

If that's correct then compare each circuit with the other using your meter and see if you can find anything that's different.

[budm]

Re: Samsung UN60D6000 LED Backlight flashing

If you disconnect the cable between the main board and the power supply board then apply the AC to the TV, then the backlghts should come on and stay on if the power supply and LEDs are good..
So does it do that at this point?
BTW, what the power supply/LED driver board P/N? BN44-??????

[ljintexas]

Re: Samsung UN60D6000 LED Backlight flashing

Thanks Bud! I was not sure if that feature applied to this model or not..
The smps is a BN44-00425A.
When I unplug the main board from the power supply..I get nothing.
When I first fired this set up..it worked perfectly..turned it on and off 12 times..so I just let it run..within 6 hrs, it was in the state it is in now. Backlights attempt to come on for a short second then go off..cycles over and over every couple of seconds. I will post a much better picture of power supply board. When it does try to fire backlights, they do come on all over, no dark spots.

Thanks for your help!

[ljintexas]

Re: Samsung UN60D6000 LED Backlight flashing

Here is a better picture of the power supply board!(courtesy of Shopjimmy)

Mine is identical. (Pic in first post)

I appreciate everyone's input!

Thanks

LJ