SAMSUNG UN55KS9000F picture fades then distorts into vertical lines after 20 seconds

[JJAAMM]

This was my main TV for the last 6 years. I'm not inclined to throw out a $2600 TV so quickly so I'm trying to investigate the issue.

Problem
TV was disconnected from power for 6 months during construction. When I plugged it yesterday picture was fine, after 30 seconds it dimmed then started developing horizontal lines, picture then starts to ghost vertically until it degrades into vertical streaks. TV always displays a perfect picture when cold. I can unplug TV for 5 minutes and plug it back in and picture is restored for 20 seconds. I can also keep it in standby mode and picture is restored temporarily when turned on cold. Issue happens across all inputs. Issue happens when one box is disconnected and TV is displaying the connect one box graphic.

Steps taken so far
I have taken the panel off to look for signs of water damage. None.
I have visually inspected all caps. No damage.
I have disconnected and reseated all ribbons and harnesses.
Inspected all ribbons.
I have disconnected the right side ribbon, and checked picture (black)
I have disconnected the left side ribbon and checked picture (same as right)
I tried randomly blocking pins with tape (never got a good picture.)
I looked at both boards under IR camera and I see no significant hot spots.

Questions
Does the fact that the picture restores after being cold indicate anything?

I have read other Samsung threads here but I'm not sure if my symptoms are exactly what other are describing as somewhat common.

Are there any tests I can perform with a multimeter?

I can buy a used main board for $50 and a power board for $20 on eBay- is it worth a try?

[Storyteller12]

Re: SAMSUNG UN55KS9000F picture fades then distorts into vertical lines after 20 seco

It’s most likely the diode pack on the buffer board of the panel.

It’s been discussed on this forum before. Try searching ks8000 or ks8500

[JJAAMM]

Re: SAMSUNG UN55KS9000F picture fades then distorts into vertical lines after 20 seco

I just bought a new main board. I assume that was a waste of money? I might be able to cancel.

[JJAAMM]

Re: SAMSUNG UN55KS9000F picture fades then distorts into vertical lines after 20 seco

I opened up the bottom of the panel to reveal the led diode buffer board and I don't see any obvious damage. I ran my IR camera and don't see any hot spots.

On the left and right side of the board I see these- how can I test them?

[Storyteller12]

Re: SAMSUNG UN55KS9000F picture fades then distorts into vertical lines after 20 seco

https://www.badcaps.net/forum/attach...3&d=1628620304

Here is pic of what the diode pack looks like.

You can measure with a multimeter or sometimes feel it get very hot with your finger.

It’s marked D003 on the very end of the buffer board

[JJAAMM]

Re: SAMSUNG UN55KS9000F picture fades then distorts into vertical lines after 20 seco

Hmm here is a video of my board. Am I missing something?

https://youtu.be/sXZxI84Gem8

[Storyteller12]

Re: SAMSUNG UN55KS9000F picture fades then distorts into vertical lines after 20 seco

Yours is sightly different. If it’s got a “D” next to it then it’s a diode. I can’t really tell from the video

[JJAAMM]

Re: SAMSUNG UN55KS9000F picture fades then distorts into vertical lines after 20 seco

Looks like none of them are labeled with a D.

I appreciate you taking the time to respond. My wife is starting to lose patience with me as every free moment I’m scouting the internet trying to get more info to troubleshoot this. It’s frustrating that the TV worked fine. It was unplugged and left in place undisturbed and this somehow happened while inert. Also, after reading similar threads am I unique in that I get perfect picture on cold startup? Also I don’t seem to have the power reboot loop.

[Storyteller12]

Re: SAMSUNG UN55KS9000F picture fades then distorts into vertical lines after 20 seco

Sorry, I looked at your pic of the board and it appears nothing is labeled.

Those ones labeled E5 maybe be diodes. Try testing them with a multimeter and see what reading you get or if any are shorted.

If you don’t have multimeter you can turn the tv on and feel if any get hot

[JJAAMM]

Re: SAMSUNG UN55KS9000F picture fades then distorts into vertical lines after 20 seco

Sorry, I looked at your pic of the board and it appears nothing is labeled.

Those ones labeled E5 maybe be diodes. Try testing them with a multimeter and see what reading you get or if any are shorted.

If you don't have multimeter you can turn the tv on and feel if any get hot

I have an infrared camera. Nothing on the board gets hot. When testing these with a multimeter, what pin to what pin am I testing?

[JJAAMM]

Re: SAMSUNG UN55KS9000F picture fades then distorts into vertical lines after 20 seco

Here is another question: there are actually two boards, left and right. Each board gets one ribbon from the main board. Would the issue not have to be up stream of the LED boards since the problem is displaying across the entire screen?

[JJAAMM]

Re: SAMSUNG UN55KS9000F picture fades then distorts into vertical lines after 20 seco

Well I replaced both the main and power boards and the issue persists. None of the diodes on the buffer panels are getting hot or looked scorched so I’m at a loss. On other models I see some people say you can just remove them, is that true?

[Storyteller12]

Re: SAMSUNG UN55KS9000F picture fades then distorts into vertical lines after 20 seco

Yes, you can just remove them to test if it’s working. It’s not recommended to keep using the tv this way if it works though

[JJAAMM]

Re: SAMSUNG UN55KS9000F picture fades then distorts into vertical lines after 20 seco

So I removed the 3 TVS diodes on the two buffer boards. Problem still exists. I also see no hotspots on my thermal camera. This was after changing out both main board and power board. I’m about to give up. What else can this be?

[Storyteller12]

Re: SAMSUNG UN55KS9000F picture fades then distorts into vertical lines after 20 seco

If you replace power board and mainboard the only thing left is the panel/ buffer boards.

You can try the tape method to see if you can get an image

[nicholas1110]

Re: SAMSUNG UN55KS9000F picture fades then distorts into vertical lines after 20 seco

I have seen this exact issue a few times on this model. It has always been a shorted capacitor on one of the buffer board. To determine the exact one just start testing the smd caps. Start on the outside edge and work in. In extreme cases where the tv works for longer than a few seconds it will actually burn a couple resistors up.

[JJAAMM]

Re: SAMSUNG UN55KS9000F picture fades then distorts into vertical lines after 20 seco

I have seen this exact issue a few times on this model. It has always been a shorted capacitor on one of the buffer board. To determine the exact one just start testing the smd caps. Start on the outside edge and work in. In extreme cases where the tv works for longer than a few seconds it will actually burn a couple resistors up.

None of them are heating up on my thermal camera. What's the best way to test?

[Storyteller12]

Re: SAMSUNG UN55KS9000F picture fades then distorts into vertical lines after 20 seco

With a multimeter set to “beep” mode. Touch leads to each side of the capacitor. If it beeps it’s shorted

[JJAAMM]

Re: SAMSUNG UN55KS9000F picture fades then distorts into vertical lines after 20 seco

Got it.

[JJAAMM]

Re: SAMSUNG UN55KS9000F picture fades then distorts into vertical lines after 20 seco

No capacitor on both boards has continuity from lead to lead. However, these all have continuity between their leads (pictured, circled in red). Are these caps?

Also, there are two caps that have no continuity to ground on either lead.