No image on QLED Samsung TV QE55Q85RAT

[jbsers]

Hello everyone

I have a QE55Q85RAT TV that no longer turns on - to be more precise, here are the diagnostic elements:

- when I turn it on, the red LED flashes once, we hear a slight "zz" twice on the motherboard, then the LED flashes twice and this cycle repeats indefinitely and no image

- taking inspiration from certain forums, I put tape on 4 tracks of the ribbon which goes from the motherboard to the panel and then, the TV still does not show any image but the sound works and the TV responds to the remote control (I turned on the voice guide) - the TV being connected to the internet, I can hear the channels.

Here are the tests I carried out with the TV running:

- I tested the voltages on the power supply card, I noticed:

350V for pin 5 which goes to the motherboard (CNM801 connector)

46.7V for Vdrv (pins 3,5,7 and 9 of connector CNV901A)

On the inverter card:

2.85V for the BLU_ON/OFF pin of the card

I can find the 46.7v on pins 9,11,13 and 15 of the CNV901A connector



Having read that the BLU-ON/OFF had to be at 5v to light the LEDs, I unplugged the Motherboard - Inverter cable and put 5v from an external power supply (batteries) on this pin - the panel did not turn on. yet not lit

I tested the 200 LEDs on the LED panel, all work.

The diodes on the power supply board work, the 2 capacitors are not bulged (nor are the small ones)

I lit the panel (front side) with a lamp but I don't see any movement through the transparency of the image.

I fear that it is the panel which is broken, yet it is only 3 years old and has not suffered any shock.

I admit that I have reached the end of the diagnostics - does anyone have any ideas on the subject?

Thank you in advance for your help.

Have a good day

[etbmikenel]

With the LEDs blinking twice you are indeed correct that the fault is located on the panel.

[jbsers]

Thanks for your reply - do you talk about led panel or Driver card ?

[jbsers]

Thanks for your reply
I have 2 questions :
1) do you talk about led panel or Driver card ?
2) if it's a driver card problem, do you think that it could have a relationship with the rubbon I had to put to have the TV starting ?
Thanks, regards

[nomoresonys]

Post clear straight on pictures of each board and one of the whole back as to see how everything is connected, expose the long thin panel driver boards if obscured from view and post a picture of that also.

[nomoresonys]

Could something as simple as what's in this video or something else, checking all the caps is a good place to start, video not in English but self explanatory: https://www.youtube.com/watch?v=Z4D41NujAcE

[jbsers]

OK thank you - after more troubleshoot actions, I discovered there is no 3,3v on T-COM board - the output of the regulator is close to 0v. I will try changing this board and will tell you.
Best