Samsung UN55D6003SFXZA not working

[notaguitarhero]

Hey everyone, I've got a Samsung TV UN55D6003SFXZA that is not working. If I unplug the TV from the outlet, wait a few minutes, and plug it back in, the startup screen ("Samsung SMART TV") appears on the screen for a second before the screen goes dark. At the same time, the standby light blinks 5 times. And then if I try to press the power button, the standby light blinks once each time.

I did a visual inspection of the power supply board and didn't find any issues. No burn marks, no capacitors that have exploded.

I disconnected the main board from the power supply board, got the backlight to turn on and stay on, and measured the voltages at CNM803:

1.) N.C. = 0V
2.) N.C. = 0V
3.) B13V = 12.74V
4.) EPWM = 3.209V
5.) B13V = 12.74V
6.) N.C. = 0V
7.) Vamp = 16.41V
8.) BLU_ON = 3.005V
9.) Vamp = 16.41V
10.) GND = 0V
11.) GND = 0V
12.) GND = 0V
13.) B5V = 5.37V
14.) A5V = 5.37V
15.) B5V = 5.37V
16.) PS-ON = 3.359V

I think it may be a main board issue? Ebay has one for $200 so I'd much rather buy a new TV.

Power Supply Board: BN4400424A
Main Board: BN94-05429D

Any help is much appreciated!

[budm]

Re: Samsung UN55D6003SFXZA not working

So far you have the correct dcv supplies and the control signals.
So the next thing you need to do is to measure the DCV at each pin of the LED connector, you will leave the black probe on the chassis, red probe on the pin THEN turn on the TV to see what the Voltage jumps up to and then wait for a few seconds to see what it drops down to then turn off the TV, then repeat that with the rest of all the pins of the LED connector.

[notaguitarhero]

Re: Samsung UN55D6003SFXZA not working

Thanks for the reply budm.

CNL802:
1.) VF+ = 328V peak, 297V steady state
3.) - = 200V peak, 177V steady state
5.) + = 210V peak, 177V steady state
7.) Dim- = 90V peak, 62V steady state

I might not have grabbed the peak voltages, but they're around those values. I took a picture of the power supply board for your reference.

[budm]

Re: Samsung UN55D6003SFXZA not working

How about pin 9 (F2), 10 (F1)?
Also if you look at the transformer TM801S' legs, you will see the through hole rivets where the four legs of the transformer are soldered too, they are know for bad solder connection, you should resolder them, same for other components that use those through hole rivets.

[budm]

Re: Samsung UN55D6003SFXZA not working

BTW, I also need a picture of the LED connector with the female connector in place so I can see how many wires are on that connector. So far it looks like it only have one big long string of LED, thus only one LED driver circuit.
Pin 3 and pin 5 should be the same since it is connected together electrically.
Vf+ pin 1 is connected to the Anode of the first LED string, the - pin 3 is the Cathode of the first LED string which is then connected to the + pin 5 which is the Anode of the second LED string, the DIM- pin 7 is the Cathode of the second LED string which is the return line to GND through the power MOSFET Q9102 and the current sensor resistor R9113 to Gnd.
So after the backlights flashes on the Voltage at VF+ is staying steady at 297VDC as long as you do not turn off the TV?
Per DC Voltage chart on the board, the LED supply Voltage is 330VDC, it sounds like you have some shorted LEDs.

[notaguitarhero]

Re: Samsung UN55D6003SFXZA not working

Transformer TM801S solder connections look good to me.

See the attachment for a picture with the LED connector in place. 4 wires on that connector coming in to Pin 1, 3, 5, and 7.

When I plug it in, VF+ reaches 328VDC, backlight is lit only for a second, and VF+ drops from 330VDC down to 297VDC as long as I don't unplug the TV.

CNL802:
Pin 1 (VF+) = 328VDC peak, 297VDC steady state
Pin 3 ( - ) = 200VDC peak, 177VDC steady state
Pin 5 ( + ) = 210VDC peak, 177VDC steady state
Pin 7 (Dim-) = 90VDC peak, 62VDC steady state
Pin 9 (IF2) = 0.6VDC peak and steady state
Pin 10 (IF1) = 0VDC steady state

If I indeed have shorted LEDs, what would be my next step?

Thanks again.

[budm]

Re: Samsung UN55D6003SFXZA not working

Can you check the resistance between pin 3 and pin 5? It should be <1 Ohm.

[notaguitarhero]

Re: Samsung UN55D6003SFXZA not working

Resistance between Pin 3 and Pin 5 on CNL802 is reading 0 Ohms.

[budm]

Re: Samsung UN55D6003SFXZA not working

Resistance between Pin 3 and Pin 5 on CNL802 is reading 0 Ohms.

That is what I thought it should be that is why it does not make sense in you DCV report on pin 3 and pin 5, they should be exactly the same since are directly tied together.
Pin 3 ( - ) = 200VDC peak, 177VDC steady state
Pin 5 ( + ) = 210VDC peak, 177VDC steady state
If it is bad LEDs, then you will have to take the panel apart to get to the LEDs, not simple job but we need to verify for sure first that it is LED problem.

[Packard93]

Re: Samsung UN55D6003SFXZA not working

SHINE A FLASHLIGHT OR BRIGHT LIGHT SOURCE if led if busted and u get pic . You know u got a backlight issue.

[notaguitarhero]

Re: Samsung UN55D6003SFXZA not working

How do I go about checking if it's an LED problem?

If I disconnect the main board from the power supply board, the screen lights up...so maybe it's not a backlight/LED issue then?

[budm]

Re: Samsung UN55D6003SFXZA not working

How do I go about checking if it's an LED problem?

If I disconnect the main board from the power supply board, the screen lights up...so maybe it's not a backlight/LED issue then?

If that is the case then the power supply/LED driver and the LED backlights are OK, I should have ask you to perform that test first, sorry about that.

[notaguitarhero]

Re: Samsung UN55D6003SFXZA not working

No worries. So it looks like the issue is the voltages dropping (approximately 30VDC drop) at the LED connector.

[budm]

Re: Samsung UN55D6003SFXZA not working

It still does not make sense to me yet as to why the backlights do come on and stay on when the main board is not connected to the power supply-LED driver but the backlights will not stay on when the connection is back in place even and all the Voltages and the Control signals are OK. I am missing something.

[notaguitarhero]

Re: Samsung UN55D6003SFXZA not working

Is it the voltage drop that is causing the backlight to turn off? They happen at the same time.

With only the main board disconnected:
CNL802:
Pin 1 (VF+) = 325VDC peak, 322VDC steady state
Pin 3 ( - ) = 162VDC peak and steady state
Pin 5 ( + ) = 162VDC peak and steady state
Pin 7 (Dim-) = 1.1VDC peak and steady state
Pin 9 (IF2) = 0.6VDC peak and steady state
Pin 10 (IF1) = 0VDC steady state


With everything hooked up (what I measured the other day, see earlier post):
CNL802:
Pin 1 (VF+) = 328VDC peak, 297VDC steady state
Pin 3 ( - ) = 200VDC peak, 177VDC steady state
Pin 5 ( + ) = 210VDC peak, 177VDC steady state
Pin 7 (Dim-) = 90VDC peak, 62VDC steady state
Pin 9 (IF2) = 0.6VDC peak and steady state
Pin 10 (IF1) = 0VDC steady state

[budm]

Re: Samsung UN55D6003SFXZA not working

The 297V will be too low. and based on that reading, the DIM pin is showing that the MOSFET for the LED return is not turn on so it shows 62VDC on the dim pin.

Are sure that:
4.) EPWM = 3.209V
8.) BLU_ON = 3.005V
Are present when the backlights go off?

[notaguitarhero]

Re: Samsung UN55D6003SFXZA not working

The 297V will be too low. and based on that reading, the DIM pin is showing that the MOSFET for the LED return is not turn on so it shows 62VDC on the dim pin.

Are sure that:
4.) EPWM = 3.209V
8.) BLU_ON = 3.005V
Are present when the backlights go off?

My apologies, I might not have clarified what the configuration was when I measured those values. The voltages measured in the original post was with the main board disconnected (where the backlight was on).

I measured the steady state values of at CNM803 with everything connected:
Pin 1 (N.C.) = 0VDC
Pin 2 (N.C.) = 0VDC
Pin 3 (B13V) = 12.71VDC
Pin 4 (EPWM) = 0.007VDC
Pin 5 (B13V) = 12.71VDC
Pin 6 (N.C.) = 12.66VDC
Pin 7 (Vamp) = 18.88VDC
Pin 8 (BLU_ON) = 0.14VDC
Pin 9 (Vamp) = 18.88VDC
Pin 10 (GND) = 0VDC
Pin 11 (GND) = 0VDC
Pin 12 (GND) = 0VDC
Pin 13 (B5V) = 5.35VDC
Pin 14 (A5V) = 5.36VDC
Pin 15 (B5V) = 5.35VDC
Pin 16 (PS-ON) = 3.30VDC

[notaguitarhero]

Re: Samsung UN55D6003SFXZA not working

To me, it seems like the issue is the main board. With the main board disconnected, the backlight lights up which probably means the power supply board and LED are fine. With the main board connected, I get the startup screen for a second or so before the voltages through the LED drop about 30VDC and BLU_ON drops to 0.14VDC.

What would be the next diagnostic to do? Check TCON?

To summarize the voltage measurements:

CNL802 (connection to LED)
With only the main board disconnected:
Pin 1 (VF+) = 325VDC peak, 322VDC steady state
Pin 3 ( - ) = 162VDC peak and steady state
Pin 5 ( + ) = 162VDC peak and steady state
Pin 7 (Dim-) = 1.1VDC peak and steady state
Pin 9 (IF2) = 0.6VDC peak and steady state
Pin 10 (IF1) = 0VDC steady state

With everything hooked up:
Pin 1 (VF+) = 328VDC peak, 297VDC steady state
Pin 3 ( - ) = 200VDC peak, 177VDC steady state
Pin 5 ( + ) = 210VDC peak, 177VDC steady state
Pin 7 (Dim-) = 90VDC peak, 62VDC steady state
Pin 9 (IF2) = 0.6VDC peak and steady state
Pin 10 (IF1) = 0VDC steady state


CNL803 (connection to main board)
With only the main board disconnected:
Pin 1 (N.C.) = 0VDC
Pin 2 (N.C.) = 0VDC
Pin 3 (B13V) = 12.74VDC
Pin 4 (EPWM) = 3.209VDC
Pin 5 (B13V) = 12.74VDC
Pin 6 (N.C.) = 0VDC
Pin 7 (Vamp) = 16.41VDC
Pin 8 (BLU_ON) = 3.005VDC
Pin 9 (Vamp) = 16.41VDC
Pin 10 (GND) = 0VDC
Pin 11 (GND) = 0VDC
Pin 12 (GND) = 0VDC
Pin 13 (B5V) = 5.37VDC
Pin 14 (A5V) = 5.37VDC
Pin 15 (B5V) = 5.37VDC
Pin 16 (PS-ON) = 3.359VDC

With everything hooked up:
Pin 1 (N.C.) = 0VDC
Pin 2 (N.C.) = 0VDC
Pin 3 (B13V) = 12.71VDC
Pin 4 (EPWM) = 0.007VDC
Pin 5 (B13V) = 12.71VDC
Pin 6 (N.C.) = 12.66VDC
Pin 7 (Vamp) = 18.88VDC
Pin 8 (BLU_ON) = 0.14VDC
Pin 9 (Vamp) = 18.88VDC
Pin 10 (GND) = 0VDC
Pin 11 (GND) = 0VDC
Pin 12 (GND) = 0VDC
Pin 13 (B5V) = 5.35VDC
Pin 14 (A5V) = 5.36VDC
Pin 15 (B5V) = 5.35VDC
Pin 16 (PS-ON) = 3.30VDC

[budm]

Re: Samsung UN55D6003SFXZA not working

OK, now it made more sense. At this point it is pointed to main board problem or something is locking out the main board from from sending the proper signals to turn on and control the backlights circuit. I would say main board is bad at this point.

[notaguitarhero]

Re: Samsung UN55D6003SFXZA not working

Yeah, I'll take a look at the main board again but I think there's not much I can do besides replacing it? It's pretty expensive and hard to find online. I'll probably just sell the parts for scrap at this point.

I appreciate all the help budm. Definitely learned a lot in the last couple of days.