samsung un65nu6900f common problem, digging deeper

[Cornito]

Ok then so, need to add the resistance between VGH and panel and test only when the jumper is removed

[lotas]

The jumper (FB_TRDY_1, FB_TRDY_3) simulates - as if we have a panel connected. When the LVDS cables are disconnected, the motherboard does not see the panel and blocks the supply voltage to the panel.

[Cornito]

I'll try to reduce the VGH Power with the resistance addition.
The masking is not working for me.
Could you just let me know what are these PIN, and why the board react like that while we shunt these two.

Regards

[lotas]

This says that you do not have a working panel, try masking (CKV...) on the non-working half, reduce the VGH power...

[Cornito]

@Iotas thank you, i works, i've soldered the jumper between these two points and my 25V is back and stable.
Could you explain me why, I need to understand

Do I need to connect LVDS cable now to see what is the behavior or do I need to perform other tests?

Thank you

Damien

[Diah]

Diah you're best Samsung seller for ever and ever 😅

i had at home never forever Samsung TV come to home... Mobile was until Galaxy S5 and no more... cause their shit cheating start after that time.

[Cornito]

Diah you're best Samsung seller for ever and ever 😅

[Diah]

What are these points?
I'll try this and let you know.

Thank you

don't do it,,, and don't buy mb too .... rubbish are rubbish and this was no 1 of fucking samsung rubbish tv

[Cornito]

What are these points?
I'll try this and let you know.

Thank you

[lotas]

Place a jumper between these points, disconnect the LVDS cable and check again that the voltage appears on VGH.

[Cornito]

There are the pictures of my motherboard.

On the motherboard I've marked the short with a black pen.
I've a doubt on a component that looks like a transistor but I'm not sure.
I can read values between all pins. 🤔
but no short as measured on caps close to 0.2ohm.

Thank you in advance.

Damien

[Cornito]

Ah that's a good information, i was not aware of.
But as I've got some caps short-cutted I need to know which one is faulty.

I'll take picture of the caps found in short, maybe the short is in the micro controller

Thank you for your support

[lotas]

In the red circle this is the coils that present short to GND, i can find some caps just under the

There is one choke and should be on the ground, since a negative voltage (-) relative to the ground is generated on this line (VOFF = VGL = VGOFF = VEEG).

[Cornito]

Don't know how to ensure panel is ok, the first steps of the issue, was a small blue line on the right side of the screen, then a complete blue line to come to this end, no picture on the screen and rebooting TV.

In the red circle this is the coils that present short to GND, i can find some caps just under the

[nomoresonys]

Can you show a picture of the shorted components.

[Cornito]

Today's Update, finally found a short to ground, attached to some caps just in the opposite side of the µC.
Some many components are in short.
I guess i need a new board, but don't know if the panel has an issue too

[Cornito]

So back with measurements results.

No short found, DC-DC supply 1.8V, 3.3V but no high voltage.
Seems that the command from µC to activate ocilator and supply the high voltages is not there.

I've measurement resistance from VGH to Ground on Driver cards, and one is over MEGAOHM the other is 5.3kOhm, guess panel issue here compatible with trick proposed in this thread.

µC becomes hot in some seconds, My bad feeling is that the µC is short cutted, but don't know how to get proof of that.
I'm still wondering cause the TV can switch in standby mode, when requested by the remote.

I don't know if I need to give up right now...

[Cornito]

Hello,

Thank you for the information. At one moment at had the feeling that the motherboard needed a feedback from drivers to supply the 25V.

So, resistance measurement on the motherboard from VGH to ground is 52 kOhm

VGH voltage is présent only when tv bootloops, LVDS un attached and / or bootloops stopped with tape method on LV0, no VGH at all.

Guess I need to focus of the VGH power supply DC to DC, transistors and capacitors on motherboard.

Thank you so much

[itelite]

Do you get anything at all on VGH? How about with no power cord plugged in, resistance to ground on VGH, and/or diode mode measurement from VGH to ground.

Best place to start would be ruling out a sort to ground, or an open circuit.

in all my test a while ago I recall there always being some kind of measurable voltage on that VGH pin/resistor.

[Cornito]

"Edited, new info at the end of the post"

Hello all,

That's a really good thing to have found this thread.
I've actually the same kind of issue With my UE58TU6905 Samsung tv.

Before moving forward with the resistor solution proposed here that seems to solve many tv.
I'd like to know if it's normal situation to do not have 25v steady on the main board when ribbon cable to drivers is unconnected?

I think that I need to get this 25v fixed before moving forward.
I get this voltage on the 22pin on my connector , when ribbon cable to driver is connected and at the beginning of the looping restart only.

Is this something that somebody already got?

Here under a picture on my main board that is a bit different of the ones shown here. I was boy able to find the resistor and nothing really clearly explained on this board

Thanks in advance for your reply.

Regards

"EDIT":
Pursuing my investigation, found one this, that the VL0 line when is isolated from the ribbon cable on the left screen side my TV stopped rebooting, only isolating this line.
But, VGH don't show any voltage output.
I've taken the resistance and found only 5.2kΩ between VGH and Ground, that seems to me a bit low.

Anybody has a feeling of i should do next?

Thanks