Samsung UN55H6203AF Suddenly Lost Picture, Now Sound

[JohnMcD348]

So, the other night, I was watching Dr Who on the DVR when the video went out. I thought it may have been a bad recording since the audio was still there. I rewound the video and it started playing again. After about 30 minutes, I heard a strange buzzing and the Video went black again. Monday Morning, No picture, No Audio.

I tried the Flashlight test and couldn't see any video

I opened the back and looked a the 3 boards. All the Caps appear OK, no bloating, no burn or browning anywhere. I've taken the boards out and made sure they were clean on the opposite side also.

When plugged in and powered on, I can see a power light on both the Main and T-Con board.

I unplugged the T-Con cables going to the LEDs individually and nothing changed on the screen.

When powered on, with all the boards connected, I do not see ANY LEDs lit.

I've watched a few Youtube videos on diagnosing the problem but nothing I've tried has really allowed me to determine definitely it is "X" board or something else. When I turn on the TV via the power button, I can see the main TV power light flash 5 times. From what I've read on the net, it may mean something but only that 1 guy in Korea who designed the TV knows for sure and it's probably a State's Secret.......

Anyway, I went to ShopJimmy and ordered their repair kit that has the 3 boards and I'll replace them when they get here. BUT, I'd really like to diagnose the problem and know what it was that caused the issue. I've never been a fan of just throwing parts at a problem and hoping it fixes it. I'd like to tinker with it before I put the new parts in.

Thanks in advance for the input. I appreciate anything you can share.

John

[Andrew F. Ali]

Re: Samsung UN55H6203AF Suddenly Lost Picture, Now Sound

1. Reconnect all the original boards as they should be for normal use.
2. Disconnect the Main Bd. from the PSU.
3. Apply the 120Vac.
4. Observe whether the Backlights turn ON and remain ON.
5. Backlight turn on and remain on, conclude the PSU is good and the Main Bd. is bad.

[JohnMcD348]

Re: Samsung UN55H6203AF Suddenly Lost Picture, Now Sound

Thanks. I'm going to say the PS is possibly bad. No lights or glow under the metal case when I plug it in and power it up with the Main Board disconnected. Also, I notice that, with the main board disconnected, and plugged in, I do not get a power light near the power switch.

But, when I plug the Main Board back in, I get the power light again and, I also notice the Optical Digital Signal lights and a Blue light is seen on the T-Con board. But, again, no white LED lights behind the screen.

Is there anything else I should check and look at to verify?

[budm]

Re: Samsung UN55H6203AF Suddenly Lost Picture, Now Sound

There will be no power lights if the cable between the main board and the power supply board is not connected that is because there will no standby Voltage to run the main board so that is normal.
So the question is , do the backlights come on and stay on when you power up the TV without the cable between the main board and the power supply board connected for sure or did you see the backlights even flash on for seconds?
We also need the pictures of the whole backside of the TV showing all the boards.
What is the power supply board P/N? BN44-00774A???
If it is then the LED strings are connected in series so if one LED goes open circuit there will be no backlights. To verify that you will have to test Voltages on the LED connector pins against GND.
https://www.shopjimmy.com/samsung-bn...led-board.htm#

[JohnMcD348]

Re: Samsung UN55H6203AF Suddenly Lost Picture, Now Sound

Hello

No Lights, no glow, nothing happens when disconnected from the main board on power up.

PS is BN44-00774A

I'll work on posting pictures soon. I just need to look up and see how this forum accommodates them.

Thanks

[JohnMcD348]

Re: Samsung UN55H6203AF Suddenly Lost Picture, Now Sound

OK, here we go.
Images of the Back of the TV. Top of the TV at Top, Power Board on Right, Main Board on Left, T-Con still under the metal housing.

Then Individual images of each board.

[JohnMcD348]

Re: Samsung UN55H6203AF Suddenly Lost Picture, Now Sound

On the power board, all of the capacitors appear good externally. The Electrolytic units don't appear bulged or burned. Same goes for the Ceramic type capacitors. They look clean with no discoloration under them on near the board.

[dick_barton]

Re: Samsung UN55H6203AF Suddenly Lost Picture, Now Sound

With the mainboard disconnected what voltages do you have on the 10 pins of CN803.
The pins are named and numbered so if you could give the pin number, name and voltage. Odd pins facing into the board and even pins away from the board.

[budm]

Re: Samsung UN55H6203AF Suddenly Lost Picture, Now Sound

Set the meter to be able to read at least 300VDC, then keep black probe of the meter on the chassis, keep red probe of the meter on pin 1 of the LED connector CNL802 (connector in place), then turn on the TV to see how high the Voltage jumps up to then wait 5 seconds to see how low it goes down to.
https://www.shopjimmy.com/samsung-bn...led-board.htm#

[JohnMcD348]

Re: Samsung UN55H6203AF Suddenly Lost Picture, Now Sound

12.78v across the top. 1,3,5,7

2 OD/UD 2.29v
4 BLU_PWM 3.23v
6 PS_ON 4.46v

AND, sure enough, I'll need to replace the board now anyway. While checking the voltages, I couldn't find my small pin leads and accidentally sparked 7/9 and 6/8 and those little metal pins don't do well when they spark.

[budm]

Re: Samsung UN55H6203AF Suddenly Lost Picture, Now Sound

So now the power supply board is dead?

[JohnMcD348]

Re: Samsung UN55H6203AF Suddenly Lost Picture, Now Sound

No, it still shows power to the pins, but after grounding them out like that, would it be a good idea to keep using it?

[budm]

Re: Samsung UN55H6203AF Suddenly Lost Picture, Now Sound

If the Voltages are still there as shown on the label then it should be OK, the protection probably kicked in fast enough to stop the damage from happening.

[JohnMcD348]

Re: Samsung UN55H6203AF Suddenly Lost Picture, Now Sound

So, do you know if those voltages look correct?

On the board, the Odds were listed at 13v so 12.78 is close. The Even wasn't listed on the board. At least, I was thinking the A13V by the 1,3,5,7 meant it was 13volts.

[budm]

Re: Samsung UN55H6203AF Suddenly Lost Picture, Now Sound

Those readings are fine.
You need to do the test on post #9.

[JohnMcD348]

Re: Samsung UN55H6203AF Suddenly Lost Picture, Now Sound

Those readings are fine.
You need to do the test on post #9.

Sorry, I missed that post.

It doesn't drop down. When I first plug it in, the voltage cycles constantly between about 284 volts and Up to 322 volts. After I press the Power Button, nothing happens, it continues to cycle within that same voltage range.

[budm]

Re: Samsung UN55H6203AF Suddenly Lost Picture, Now Sound

Sorry, I missed that post.

It doesn't drop down. When I first plug it in, the voltage cycles constantly between about 284 volts and Up to 322 volts. After I press the Power Button, nothing happens, it continues to cycle within that same voltage range.

The LED driver is not see the LED load, if you look at the LED DRIVE Voltage chart you will see '268V 380mA', when it does not see the load the output Voltage will go way up above the rated Voltage with load.
So you have open circuit some where from the connector to the LCD panel and back to the board.
Do you have LED tester to test the LED strings?

[JohnMcD348]

Re: Samsung UN55H6203AF Suddenly Lost Picture, Now Sound

No.
So I need to go deeper into the case and expose the actual LED strips? Is there any specific point between the LEDs and the actual LCD panel I should look at?

Thanks

[budm]

Re: Samsung UN55H6203AF Suddenly Lost Picture, Now Sound

Do you see the LED connector pin's chart? As you can see you have M1+ which is the Anode of the first LED string, the M1- is the Cathode of the M1 string which is connected to the M2+ of the second string, M2- is the Cathode of the M2 string which is then connected to M3 +, and so on to form one large LED string, it is like having 5 set of Christmas connected in series.
What you can do is to test rest of the LED connector pins to find out where the open circuit is at which string of the LED.
If you understand series circuit then when you see the test result you can see where the open circuit is at.

[Andrew F. Ali]

Re: Samsung UN55H6203AF Suddenly Lost Picture, Now Sound

Hmmmm...does seem that the PSU is good at but the LED Driver circuit could be faulty or you have an open string/s of LEDs. If the voltage at M1+ goes to the 263V and then drops low and the M- is at 0V that would indicate bad LEDs. Voltages would be measured WRT chassis GND.