Samsung TV won't turn on ... keeps cycling the power relay on & off

[Journey11]

Hi All,
First time posting here ... my name is Kevin but my friends call me Journey.
I have a Samsung 75" LCD model UN75RU8000FXZA that I don't remember the original fault other than it wouldn't power up anymore.
After it sat for many month's I decide to look at it again. The motherboard seemed to have power regulation issues. After much fussing I decided to just get a new MB.
It came a few days ago and I installed it now just cycles the power relay on and off ... when on the backlights light up and then dim and then relay kicks off and the whole things starts again.
Also no standby light. I saw a couple you tube vids with same issue and they just replaced MB and problem solved ... mine apparantley different story.
I called the shop who sold the board to me to get a history of this MB ... whether used or new and I think he said they got new from Samsung.
Anyway, he told me that no standby light is the issue and said the power for that comes from the power supply board which it does not.
That power button and LED plug into the MB. I rechecked the PS board for correct voltages and it looks good so I can't see where the problem might be.
Any ideas would be helpful ... thanks in advance

Journey

PS if any pics are requested I will accomodate.

[ResetReality]

Disconnect the screen connector lvds cable....does it stay on?

[Journey11]

I'll give that a try ... thanks.

[Journey11]

Hello Reset,
Well I tried your suggestion and something happened. First tried both ribbons discoed and lo & behold it stayed on. So then tried connecting just one ribbon and it stayed on. Both connected back to cycling on/off again.
Then tried one again but the other side this time and it stayed on again. So the three times it stayed on there was only back lights on and checked the standby LED on the front and it didn't seem to be doing anything.
Included are some pics of the rig.

So at 1st I thought the first disconned ribbon was a bad side of either the screen or the pcb that attaches to the screen and the ribbon. But that didn't hold up as the side I thought might be bad/toast was then connected and the other side not it stayed on. SO it's only when both ribbons are connected that it cycles again.

[lotas]

You first need to install the jumper, and then experiment with lvds tapes.

[Journey11]

What's the jumper for or do and what am I looking to see or find ?

[lotas]

What's the jumper for or do and what am I looking to see or find ?

The jumper creates feedback between the motherboard and the panel, when any lvds cable is disconnected, the connection between them is lost and the motherboard blocks the supply voltage for the panel at the t-con. When you install the jumper, you deceive the motherboard (as if the panel is connected) and now you can disconnect one cable at a time. check which half creates the defect.

[Journey11]

Great Thanks ... but if you didn't notice in the pix ... this unit doesn't have a separate T-Con, just the long strips that run along the bottom of the screen.
I'll let ya know what I find.

[lotas]

I am aware that modern Samsung models have t-con built into the motherboard.

[Journey11]

Hi I'm Back,
Well did the jumper trick and got one side of TV to display (Right side) When left side connected I get darkish screen backlit but no image. I'm guessing the screen is shot ?
Remember no separateT-Con. Or is there a component that can be isolated on the long pcb strip along the bottom of the screen the attaches to the screen ?

[Journey11]

Hi Reset,
One thing the original owner said ... the TV was barely a year old. I can't imagine the screen died after only a year ?

[nomoresonys]

Can you post some good clear pics of "long pcb strip along the bottom of the screen" maybe someone can help from there.

[EazyBone]

Edit oops