UE55D8000 Power Cycling On Off Issue

[mrdiy88]

Hi Guys,

I have a Samsung UE55D8000 with an issue of power cycling. The TV would have come on and start to cycle after a while. It used to come on for perhaps 15 minutes then start to cycle.

I disconnected the main board from the power supply and it stopped cycling so I thought then that the issue was with the main board. The votages on the power supply tested ok.

So I then ordered up a main board BN41-01622C (BN94-04313T) and carefully replaced the old main board. I was gutted to see when I turned it on that the power cycling issue is still there.
The LED lights come on, then off and I can hear the relay clicking on and off. All caps look perfect on the Power board.

Can anyone suggest where I go from here? This has been driving me crazy and I would love to get this set fixed.

Cheers guys!

[nomoresonys]

Re: UE55D8000 Power Cycling On Off Issue

Could be a backlight issue, the replacement mainboard might be bad.

[mrdiy88]

Re: UE55D8000 Power Cycling On Off Issue

Thanks, I will test the backlights just in case, although when it was working they all looked good. The main board I bought was sold as fully tested and it was packed very well so I am hoping it wasn't bad (I doubt it) but will test on further. If you have any other advice fire away

Thanks

[nomoresonys]

Re: UE55D8000 Power Cycling On Off Issue

Can you post really good detailed pictures of the top and back of the mainboard?

[daz2206]

Re: UE55D8000 Power Cycling On Off Issue

check the cable between psu and mainboard, i had the same problem with a ue55es8000 (year younger model) and it was the connecting cable shorting (mine was burned in the pin holes)

[mrdiy88]

Re: UE55D8000 Power Cycling On Off Issue

I will do this now, I have checked the pins though I didnt notice any shorts on the 13v side or anything, they look good. Will post images now, thanks guys

[mrdiy88]

Re: UE55D8000 Power Cycling On Off Issue

Here is the images of the main board hopefully all clear enough

[nomoresonys]

Re: UE55D8000 Power Cycling On Off Issue

How bout some good clear pics. of power supply board, just the top should be good for now, just for testing.

[nomoresonys]

Re: UE55D8000 Power Cycling On Off Issue

See if you can get a good picture of the little legend/map with the expected voltages also.

[nomoresonys]

Re: UE55D8000 Power Cycling On Off Issue

You do have a multimeter for testing?

[mrdiy88]

Re: UE55D8000 Power Cycling On Off Issue

Here is the Power supply images and the legend. I do indeed have a multi meter. Thanks

[nomoresonys]

Re: UE55D8000 Power Cycling On Off Issue

Hmmmm, I wonder if there's an easy way to test the backlights on this model?

[mrdiy88]

Re: UE55D8000 Power Cycling On Off Issue

Thats what I was hoping. I'm not sure the best way to go about it. Although with the led connectors removed it still cycles off and on endlessly.

I am making it my mission to get this one fixed if its the last thing I do lol

[budm]

Re: UE55D8000 Power Cycling On Off Issue

Can we at last see the pictures of the whole backside of the TV so we can see how all the boards are connected together?

[mrdiy88]

Re: UE55D8000 Power Cycling On Off Issue

No problem. Here is the image showing the back. Thanks

[budm]

Re: UE55D8000 Power Cycling On Off Issue

Power supply- LED driver board BN44-00428A, same as used in UN55D7000LFXZA.
Disconnect the cable between power supply and the main board then plug the AC plug into the outlet and see if the backlights will come on and stay on or flash on for seconds.
Pictures provided by shopjimmy.

[mrdiy88]

Re: UE55D8000 Power Cycling On Off Issue

I can confirm that from disconnecting the cable going from the power supply to main board the tv does not cycle on and off and the leds do not light at all. It clicks once as if the power supply is on but no leds light at all. Many Thanks

[budm]

Re: UE55D8000 Power Cycling On Off Issue

So you are 100% sure that the backlights did not even flash on for seconds at all, correct?
There are 4 sets of LED Voltage booster circuits (for 8 strings of LEDs)so if we have one bad string, the backlights should flash on for seconds then the error detection circuit will kick in and shut down the backlights circuits. There are many threads about BN44-00428A in Badcaps.

[budm]

Re: UE55D8000 Power Cycling On Off Issue

BTW, you should also try re-soldering the transformer pins and devices' leg, especially those that are soldered to the through hole rivets.

[mrdiy88]

Re: UE55D8000 Power Cycling On Off Issue

With the cable to the main board removed they do not flash at all when ac is switched on. I can hear the relay click on but definately not even a flash