Samsung UN55MU6290 - No Power, No Standby Light

[egge88]

Hello my Samsung UN55MU6290FXZA recently is showing no function and I've gone through what makes sense to me, but I'm in need of a recommended next step.

TV symptoms are No picture and no standby light. When the CNM8003 is disconnected to the main board the back-light does illuminate.

Testing the CNM803 connection with the main board connected provides the following.
Pin / Signal / Voltage Reading
1 / Fail Count / 0.0V
2 / ANA DIM / 0.0V
3 / A13V / 9.09V
4 / OD On-OFF / 0.0V
5 / A13V / 9.09V
6 / PWM BLU / 0.0V (can't read PWM signal with my tools)
7 / A13V / 9.09V
8 / Power ON / 0.0V
9 / A13V / 9.09V
10 / GND / 0.0V
11 / GND / 0.0V
12 / GND / 0.0V


Testing the CNM803 connection with the main board disconnected connected provides the following.
Pin / Signal / Voltage Reading
1 / Fail Count / 0.0V
2 / ANA DIM / 2.73V
3 / A13V / 12.9V
4 / OD On-OFF / 3.67V
5 / A13V / 12.9V
6 / PWM BLU / 3.07V (can't read PWM signal with my tools)
7 / A13V / 12.9V
8 / Power ON / 4.0 V
9 / A13V / 12.9V
10 / GND / 0.0V
11 / GND / 0.0V
12 / GND / 0.0V

From this information I assumed there was some issue with the power supply board (could not provide the needed current to the main board) or there was some issue on the load from the main board, so I ordered replacements for both. Main Board. Power Supply

The main board arrived first, replaced and I have the same symptoms. Replaced the power supply board also, same symptoms. I've tried the other combinations of components and every time I get the same result with minor variations of voltages. I have trouble believing a purchased component would come in with exactly the same issue. I'm more concerned that the power supply had some unexpected behavior and burnt the replacement main board.

I'm quite confused and what could be my issues. For giggles I tested the voltage at the main-board where the power button and IR receiver come in. At appears that the main board is receiving the communication from both the physical switch and the remote to power on.

Pin / Voltage in Nominal / Voltage When power Button Is Applied to remote or TV
1 / 3.3V / 2.7V (Remote)
2 / 0V /0V
3 / 3.39V / 3.39V
4 / 0V / 0V
5 / 0V / 0V
6 / 1.87V / 0.0 (TV, Physical power button)
7 / 1.87V / 1.87V
8 / 0.0V
9 / NC
10 / NC
11 / 0V
12 / 0V


I would very much appreciate any recommended investigations or insulting comments toward obvious mistakes that will end the complaining from my SO.

-Andrew-

[CapLeaker]

Re: Samsung UN55MU6290 - No Power, No Standby Light

For shits and more giggles, unplug that wifi module and see what happens.
Your replacement main board isn’t the same as the original. The MU has tons of different versions. Check SJ.
The PSU you tested correctly by unplugging the main board and the back lights came on. It’s a main board fault or something connected to the main board that is at fault.

[egge88]

Re: Samsung UN55MU6290 - No Power, No Standby Light

For shits and more giggles, unplug that wifi module and see what happens.
Your replacement main board isn't the same as the original. The MU has tons of different versions. Check SJ.
The PSU you tested correctly by unplugging the main board and the back lights came on. It's a main board fault or something connected to the main board that is at fault.

Thank you for the feedback. I unplugged the wifi module and the Voltages are the same. I did the same with everything unplugged from the main board. Same result as well

Testing the CNM803 connection with the main board connected and WIFI module unplugged provides the following.
Pin / Signal / Voltage Reading
1 / Fail Count / 0.0V
2 / ANA DIM / 0.0V
3 / A13V / 9.09V
4 / OD On-OFF / 0.0V
5 / A13V / 9.09V
6 / PWM BLU / 0.0V (can't read PWM signal with my tools)
7 / A13V / 9.09V
8 / Power ON / 0.0V
9 / A13V / 9.09V
10 / GND / 0.0V
11 / GND / 0.0V
12 / GND / 0.0V

Shop Jimmy suggested that the BN94-12640P is a substitute for BN94-12608A here. I actually ordered the BN94-12608A but the BN94-12640P was delivered. Either way, I can't find either of these board in stock anywhere else to purchase a third.

[notallbad]

Re: Samsung UN55MU6290 - No Power, No Standby Light

When you say tested voltages with everything disconnected did that include the 2 ribbon cables to the T-con/panel?

[nomoresonys]

Re: Samsung UN55MU6290 - No Power, No Standby Light

You want to see if pins 6 and 8 change value when you hit the power button so with everything hooked up test them in standby which is tv plugged in then just hit power on and see if the values change and make note of what the voltage is.

[egge88]

Re: Samsung UN55MU6290 - No Power, No Standby Light

When you say tested voltages with everything disconnected did that include the 2 ribbon cables to the T-con/panel?

Yep, T-Con disconnected as well as pictured here.

[notallbad]

Re: Samsung UN55MU6290 - No Power, No Standby Light

CN18C1??? On main board, what is that it connects to???
IR sensor pcb at the bottom and keypad mini joystick/ or reset button just above it?

Also further along that edge of the board are 5 test points,
EEPROM SCL
Syb_Reset
EEPROM VCC
fa net rx??? (cant quite read it)
Sw power delay 2

I think you should go back to your original main and power board and continue with testing etc...

[egge88]

Re: Samsung UN55MU6290 - No Power, No Standby Light

CN18C1??? On main board, what is that it connects to???
IR sensor pcb at the bottom and keypad mini joystick/ or reset button just above it?

Yes, that CN1601 connects to the IR receiver and a combination power and navigation button array. See attached picture for a close up.

Also further along that edge of the board are 5 test points,
EEPROM SCL
Syb_Reset
EEPROM VCC
fa net rx??? (cant quite read it)
Sw power delay 2

I think you should go back to your original main and power board and continue with testing etc...

So far I've completed the testing on both sets (original and replacement) but fair point to isolate. I can't find a good detail of the circuits on the main board to understand what I'm testing and what the test would be on.

I've attached two more images showing this area of the board surrounding the CN1403 and CN1601.

[CapLeaker]

Re: Samsung UN55MU6290 - No Power, No Standby Light

Even with a bad eeprom, the stby led should be still on. I wonder if that joystick ir receiver combo is any good? Try to see if something shorted there. Other than that this doesn’t make any sense, unless you got 2 bad main boards. It shouldn’t happen, but once in a while it does, even with SJ. Speakers are disconnected too?
Can you provide any history on that tv?

[egge88]

Re: Samsung UN55MU6290 - No Power, No Standby Light

The IR sensor and the power/joystick can be unplugged individually. Isolating each and trying to power on has the same result as before, no led, no backlight, and no change in 9V from the powersupply.

Pin / Voltage in Nominal / Voltage When power Button Is Applied to remote or TV
1 / 3.3V / 2.7V (IR)
2 / 0V /0V (IR)
3 / 3.39V / 3.39V (IR)
4 / 0V / 0V
5 / 0V / 0V
6 / 1.87V / 0.0 (TV, Physical power button)
7 / 1.87V / 1.87V(TV, Physical power button)
8 / 0.0V
9 / NC
10 / NC
11 / 0V
12 / 0V


CNM803 shows no change in any signals when pressing the power button on the remote or the TV chassis.(Pin 6 and 8 are constantly at 0V)

What I don't understand is why the power supply is only providing 9V? The standby voltage on the board is showing 8V, but changes from 12.9V when CNM803 is unplugged to 9.05V when CNM803 is connected. I'm getting the sense something is up with the main 2x boards.

I've gone over the a few test points that I thought could be interesting on the main board and in general I'm only finding on test point active.

FA-NET TX - 3.4V
FA-NET RX - 3.4V
TEST_PR - 0.0V?

[egge88]

Re: Samsung UN55MU6290 - No Power, No Standby Light

Sorry, the TV is mine. 3 years without any major incident. Woke up the next morning to a non-functional TV. Today, I've come to learn that a few outlets in my house are not grounded. The entertainment system surge protector plug being one of them. No other products in the house are showing any issues.

[nomoresonys]

Re: Samsung UN55MU6290 - No Power, No Standby Light

I think you did get a bad one from SJ, send it back and they'll send you another if they have it. What else could it be?? Unless it's the cable from powerboard to mainboard.

[CapLeaker]

Re: Samsung UN55MU6290 - No Power, No Standby Light

yeah... bad replacement board.

[egge88]

Re: Samsung UN55MU6290 - No Power, No Standby Light

Replacement main board board 2.0 came in today. Hooked up and now we have a new situation.

Standby LED is illuminated. When the power button is pressed (Remote or button) the TB attempts to boot with a second or two of back light, then backlight goes away and seems to start a boot loop cycle about every 10 seconds or so.

Loop is:
1-2s backlight activated (9V standby changed to 12.9V)
2-10s backlight drops out, (12.9V drops significantly and comes back up to 9.09V

Nothing really changes by unplugging the Tcon, wifi module, or IR/power nav (using the other to power on)

I'm assuming this is EEprom or some other issue which I'm not familiar with correcting. Any recommendations with this other failure mode?

[brucetv]

Re: Samsung UN55MU6290 - No Power, No Standby Light

Turn the tv off and unplug one ribbon cable from the main board to the panel and turn it on and see if it stays on without turning on and off in a boot loop. If it does stay on turn the tv off. Wait about 5 minutes and then hook that cable up and unhook the other ribbon cable to the panel. Turn it on. If it boot loops then you have a short in the lower driver board on that side of the panel. A common fault on both the 55" and 65" MU models. This is a tedious repair involving a capacitor or two on that driver board that are in parallel so it takes a lot of time to find it. This is the result of Samsung's attempt to eliminate the tcon board to save money and allows a surge to take out these tiny caps instead of a tcon board. We are seeing this so often now we just refuse the repair due to the bench time involved in doing it right. And now Samsung's Display has announce they will no longer manufacture panel's for Samsung and sent Samsung begging back for mercy at Sharp for panels. What are you thinking Samsung? Just pay more for the panels from Samsung Display so they can make a profit instead of going back to Sharp panels that can't perform. And then to make things worse Samsung announced they will end their agreement with Kateeva for their new QD Oled film technology development that looked promising and put Kateeva nearly out of business. Don't be surprised if TCL or Hisense swoops in like a vulture with a claw full of cash and buys Kateeva or it's technology giving them the edge for the first QD Oled before Samsung's engineer's have a chance to breath, and then cry.

[egge88]

Re: Samsung UN55MU6290 - No Power, No Standby Light

Thank you for the insight. I checked the operation with individual ribbon cables. In either condition the unit still continues to boot loop. I also checked with no ribbon cables, same boot loop.

[CapLeaker]

Re: Samsung UN55MU6290 - No Power, No Standby Light

I guess you got another bad main board. Send it back and get another one. Maybe try to update firmware?

[egge88]

Re: Samsung UN55MU6290 - No Power, No Standby Light

I'm searching again and the only main boards I can find available are >$250. All of my known reputable vendors are out of stock. I assume there are many issues with this main board. For me the cost doesn't make financial sense to keep this TV alive. I'll look for someone local that wants scrap parts.

Thank you all for your support. I appreciate the guidance and sharing of knowledge!

[nomoresonys]

Re: Samsung UN55MU6290 - No Power, No Standby Light

Wonder if that's a match??: https://www.ebay.com/itm/Samsung-BN9...UAAOSwWfda33vt

[nomoresonys]

Re: Samsung UN55MU6290 - No Power, No Standby Light

More there: https://www.ebay.com/itm/Samsung-UN5...ry!43616!US!-1