Samsung UE60KU6079 backlight okay mainboard responsive, no picture, no sound

[Ierwin]

Hello everyone,
Ive got a UE60KU6079 on the workbench that is giving me some headaches trying to troubleshoot.
The previous owner stated that there had been white dots on the screen which from the description sounded like some lenses fell of the backlight LEDs.
He had opened the TV from the back, trying to get to the backlight, supposedly gave up, reassebled everything and gave the TV to me.
I expected the worst like ripped COF cables or a cracked panel but could not find anything like that yet.
Anyway I still fully expect that there has been something seriously damaged about that panel, but I am here to understand whats going on.
What is really putting me off is the fact that there is no sound. With a damaged panel I would either expect a boot loop or working sound.
But maybe that expectation is wrong for the particular model?

Heres what I see step by step
- the device reacts to the power button on backside and remote
- backlight turns on full brightness and dimms down a little after a second during boot
- device stays on, no boot loop
- screen stays black
- Unplugging either side of the screen cables from the mainboard (no seperate T-Con on this one) does not produce a half picture
- Plugging a HDMI source (FireTV Stick) into HDMI1 makes the TV react with change s in the backlight brightness

As I said, I would put my money on the panel beeing damaged given the history of someone with no experience working on such a big screen, if only there was sound.

I plan to spend some more time to inspect the panel in daylight and look for clues of physical damage.
If anyone has any idea what else I could try, I would love to hear.
For example is it possible that this particular model shuts off sound when a damaged or disconnected panel is detected?

Best regards

Ier

[lotas]

- Unplugging either side of the screen cables from the mainboard (no seperate T-Con on this one) does not produce a half picture

And it will not give any image, since when you disconnect any cable to the panel, you disrupt the feedback (T-CON - panel) and T-CON blocks all output voltages to the panel, you need to install a feedback jumper between the control points FB_TRDY_1 and FB_TRDY_3.

[bohaboha]

And it will not give any image, since when you disconnect any cable to the panel, you disrupt the feedback (T-CON - panel) and T-CON blocks all output voltages to the panel, you need to install a feedback jumper between the control points FB_TRDY_1 and FB_TRDY_3.

Is it true that if you test those control points FB_TRDY_1 and FB_TRDY_3 and there is 3V then it is a faulty Screen?

[lotas]

Is it true that if you test those control points FB_TRDY_1 and FB_TRDY_3 and there is 3V then it is a faulty Screen?

I didn't understand anything, where can I see 3v? T-CON outputs several different voltages to the panel...

[Ierwin]

you need to install a feedback jumper between the control points FB_TRDY_1 and FB_TRDY_3.

Have not found those points yet, but I will continue to look for them.

I realized that the panel was sitting a bit odd in the frame and removed the front frame. I suspect that the tv had been tiltet upright with the back side removed and the panel slid down about 1cm due to its weight.
Still have not seen any signs of cracks, but theere has definetly been some stress on the COF cables on the side of the screen. NOthing to bad, but some were kinked a bit.
From how flimsy these things are I suspect the stress of the panel weight essentially pulling down on the side cables could have been enough to cause problems to an ontherwise perfectly good panel.
Its sad that this happened when the solution to the original problem with wgite dots would have been so easy.

[Ierwin]

I connected TP_TRDY_1 and TP_TRDY_3 but still not get any picture with one side disconnected.
I also did a closer inspection of the COF on the side of the panel and indeed found visible damage on the topmost one on the left panel side.
Its hard t get a sharp picture because its so tiny but it looks like the foil teared.
If there is a broken line in that COF foil I am affraid I do not have the tools nor the skill to fix them.

I will try to get a better look at these things later.

[bohaboha]

I didn't understand anything, where can I see 3v? T-CON outputs several different voltages to the panel...

Hi I mean in the investigation process if you find on those points 3V then you have the error on the screen wondering if this statement is true?