Samsung UN40D6400UFXZA Power Cycles

[twilliard]

My Samsung UN40D6400UFXZA Power Cycles (click on and off) you can just see the smart TV logo show then turns off, TV Keeps cycling

Power Board PD46b2_BDY Code: BN44-00427B

HELP!!

[twilliard]

Re: Samsung UN40D6400UFXZA Power Cycles

No bulging capacitors

[tibimakai]

Re: Samsung UN40D6400UFXZA Power Cycles

Dose days are gone, when capacitors were the fault.
I'm thinking mainboard.
If do you disconnect the wire harness between power supply and mainboard, the TV turns on and has backlight?

[twilliard]

Re: Samsung UN40D6400UFXZA Power Cycles

When I unplug the wire harness between power supply and mainboard

You can hear a relay click one time( does not cycle) but no backlight

[twilliard]

Re: Samsung UN40D6400UFXZA Power Cycles

link to video of tv power cycling

https://www.dropbox.com/s/mx3zqa7j6c...53728.mp4?dl=0

[twilliard]

Re: Samsung UN40D6400UFXZA Power Cycles

Link above bad

New updated Link

https://www.dropbox.com/s/60gjk19uqf...53728.mp4?dl=0

[budm]

Re: Samsung UN40D6400UFXZA Power Cycles

Inspect the power supply board real well, especially the solder joints of the transformer legs and the legs of the MOSFETs and Diodes mounted on the heatsinks.
Also list the DC Voltage readings of each pin with its name of the connector CNM802, there is a chart that lists the pin out of the connector, check them when TV is plugged in but power switch is not activated, and when the power switch is activated.

[twilliard]

Re: Samsung UN40D6400UFXZA Power Cycles

Main Board unplugged reading taken on Power Board

Pin # Label Voltage My Reading

7 ---- 13V --- 12.77

9 --- 13V --- 12.77

10 --- 13V --- 12.77

17 --- 5v --- 5.33

18 --- 5v --- 5.33

19 --- 5v --- 5.33

[tom66]

Re: Samsung UN40D6400UFXZA Power Cycles

Do you see a pin marked "BL ON" or "ON/OFF"? Check that too.

[twilliard]

Re: Samsung UN40D6400UFXZA Power Cycles

PIN LABEL My readingPIN LABEL My reading
2 PWM4 0 1 OD_LE 2.68
4 PWM3 0 3 OD_ON 3.16
6 PWM2 0 5 GND 0
8 PWM1 0 7 B13V 12.77
10 B13V 12.77 9 B13V 12.77
12 BLU 2.89 11 Vamp 12.77
14 GND 0 13 Vamp 12.77
16 GND 0 15 GND 0
18 A5V 5.33 17 B5V 5.33
20 PS 4.11 19 B5V 5.33

[twilliard]

Re: Samsung UN40D6400UFXZA Power Cycles

PIN__ LABEL__ My reading
1__ OD_LE__ 2.68
3__ OD_ON__3.16
5__ GND__ 0
7__ B13V__ 12.77
9__ B13V__ 12.77
11__ Vamp__ 12.77
13__ Vamp__ 12.77
15__ GND__ 0
17__ B5V__ 5.33
19__ B5V__ 5.33

PIN__ LABEL__ My reading
2__ PWM4__ 0
4__ PWM3__0
6__ PWM2__ 0
8__ PWM1__ 0
10__ B13V__ 12.77
12__ BLU__ 2.89
14__ GND__ 0
16__ GND__ 0
18__ A5V__ 5.33
20__ PS__ 4.11

[tw2005]

Re: Samsung UN40D6400UFXZA Power Cycles

Looks the same fault as a 55D7000, defective LED strips. Could be mainboard but I know with mine i proved open cct section of strip. Mine had a 4 channel LED cct, none blown but suspect joints. Disconnecting the backlight leads on mine created the same relay cycling. managed to bypass the LEds broken and it ran for 6 hours then I think they were burnt out.

Just for info, I have lttle experience with LCD.

[budm]

Re: Samsung UN40D6400UFXZA Power Cycles

OK, pin 20 PS (PS_ON, 4.11VDC), is it steady or it is fluctuating in sync with the power cycling?
Do you also hear the power relay RL801S clicking in sync with power cycling?
This TV has 4-channel LED driver circuits.
Did you check the solder joints on the bottom side of the board? see the red circles in the picture.
I also marked the bottom side of the board to show the function of each section of the board based from what I can see from the picture provided by shopjimmy.

[tibimakai]

Re: Samsung UN40D6400UFXZA Power Cycles

To me, it seems like on the right side, the LEDs don't turn on.

[twilliard]

Re: Samsung UN40D6400UFXZA Power Cycles

OK, pin 20 PS (PS_ON, 4.11VDC), is it steady or it is fluctuating in sync with the power cycling? -- fluctuating in sync



Do you also hear the power relay RL801S clicking in sync with power cycling? -- YES


Did you check the solder joints on the bottom side of the board? see the red circles in the picture.-- Yes Re-Soldered All

I found this on the main board





1) what is it

2) is it bad (does not look good to me)

Thank you for all the help trouble shooting this

[budm]

Re: Samsung UN40D6400UFXZA Power Cycles

OK, so the main board is sending out Pulse on the PS_ON line instead of steady DC.
Is the V5B and B13V also fluctuating?

https://www.badcaps.net/forum/attach...1&d=1417811352
That is the small inductor with a hole on the shrink tubing, it does not look burnt out.

[twilliard]

Re: Samsung UN40D6400UFXZA Power Cycles

Is the V5B and B13V also fluctuating? Yes in Sync with the clicking

[twilliard]

Re: Samsung UN40D6400UFXZA Power Cycles

Is the V5B and B13V also fluctuating? Yes in Sync with the clicking

[budm]

Re: Samsung UN40D6400UFXZA Power Cycles

OK, now it makes more sense now, the standby power supply is not stable, it can be due to bad caps on the power supply board or the main board is drawing too much current.
You can run the power supply board by itself and use the 10 Ohms 5W resistor to simulate current draw of 0.5A on the V5B output, it should be able to maintain 5V output with 10 Ohms load.

[twilliard]

Re: Samsung UN40D6400UFXZA Power Cycles

I do not have a 10 Ohms 5W resistor is there anything else I can us

sorry I am new to this!!