Samsung TV UN75NU7100/Power Board BN44-00874C

[nomoresonys]

Changing out the rest of those electrolytic caps is easy and might just solve it but you may have already fixed the powerboard with the work you have done.

[nomoresonys]

I hate to guess but I would say you have a backlight issue, probably one or more bad leds.

[Larrob19]

No I don't have a backlight tester. When the backlights come on they are all on. When I plug the PB back in the relay clicks, they come on bright then go dimmer then they go off, the relay clicks and it starts over.

[EazyBone]

Post a video of it on YouTube and give us the link here. It's hard to tell if you have a rebooting Samsung or you have an actual power board problem

Edit is the red link blinking 2x stops then blinks 2x and repeats?

[Diah]

OK, I tried it without the lamp, the relay clicked and the LEDs came on dim, then went bright then the relay clicked and they went off. Then started all over again. Next step?

do it again with out screen

[Larrob19]

EasyBone, If you mean the Red power light at the bottom of the screen, it flashes once then starts the sequence over again.

Diah, I don't know what you mean without the screen.

[Diah]

EasyBone, If you mean the Red power light at the bottom of the screen, it flashes once then starts the sequence over again.

Diah, I don't know what you mean without the screen.

disconnect one lvds cable a time between mainboards and screen

[Larrob19]

I disconnected 1 ribbon cable at a time then both at once and they do the exact same thing as in Post #23.

[EazyBone]

Oh yes my bad. Mainboard is disconnected. Disregard what I said. I'm confusing myself. As Sony said PB or LEDs. Common it's LEDs on these tvs. Good luck

[Larrob19]

Here is a link to a video as to what the tv is doing. Backlights flashing on and off.

[Larrob19]

Woops forgot the link. https://youtu.be/HqdbFdniHEs

[Diah]

disconnect the main boards from the power boards and turn it on... if the BL remain on... then you have issue at MB, but if the same BL on and off then Power boards or the LED BL

[EazyBone]

Says the video is private. Can't open it

[Larrob19]

Try this link. https://youtu.be/HqdbFdniHEs?si=zNtNsFCGEBgiMN0_

[EazyBone]

I see it now. Yes can be PSU or LEDs as stated above. Led tester works great on LEDs.

Can also pull the PSU out of circuit and plug it in, test the voltages at the led connector.

My bet is it is the LEDs.

[Larrob19]

I just realized that video I posted was with the MB disconnected. This link here is with all boards connected.
https://youtube.com/shorts/Bqnl02fAh...4taZia97O6lkOZ

[EazyBone]

So much is going on here lol. Throw this thing away


Keep everything connected. Disconnect the ribbons from the main to the panel. What happens?

[Larrob19]

Already did that. See post #28 and #23. Starting to look like a recycle project.

[EazyBone]

I literally just picked up this exact tv well I have the 710d model that has a TCON and it is flashing the LEDs on and off. Same PSU. Doing some testing but I'll get back when I figure some stuff out.

As a note all my LEDs test good and when I turn it on the LEDs flash on and off and relay repeatedly clicks.

I can't get voltages at the LEDs from the PSU. Looking like it's something with PSU, I'll do some testing over next couple days

As an additional note, no mosfets were blown on this board. The original owner said it flashed on and off. The picture shows up and flashes on and off. So I at least have picture

[EazyBone]

And out of pure luck I have a broken one that I may be able to repair. This one has those same mosfets you had blow. Let's see what happens