Samsung UN55KS800DFXZA Ver. AA02 with the seemingly common power cycling problem

[Kilroy2k1]

Re: Samsung UN55KS800DFXZA Ver. AA02 with the seemingly common power cycling problem

I pointed to the diodes as a potential point of fault, I do not recommend just removing them willy nilly without finding the 1 thats faulty.
You can narrow down what side the fault is on by reattaching the flex one side at a time.
Once thats sorted, you can try the lighter fluid method or sharpen your probes and test them, If they test ok then it could be a capacitor. test for a shorted cap as well.
I wish i would have taken video of the one I located the faulty diode on, it was like watching a liquid heartbeat.

[SoftwareHack]

Re: Samsung UN55KS800DFXZA Ver. AA02 with the seemingly common power cycling problem

No, I planned on figuring out which component is bad before looking at removing/replacing it. I've read that this kind of issue tends to happen on each end boards, but I'll see if it is isolated to just one.

I saw a video of the lighter fluid technique and it did look like a heartbeat on top of one of the IC's. Now, I have to find some lighter fluid.

[SoftwareHack]

Re: Samsung UN55KS800DFXZA Ver. AA02 with the seemingly common power cycling problem

So, the power cycling happens only with one of the sides is connected so I'll start looking there.

[Nick's Tvs]

Re: Samsung UN55KS800DFXZA Ver. AA02 with the seemingly common power cycling problem

If your resistors are good then find the shorted bank of diodes on the ends of the outter boards.

They will be shorted. PS they are all in parallel I believe. I don't have the TV anymore so I can't double check but all will appear shorted I think even though not all are bad.

[Kilroy2k1]

Re: Samsung UN55KS800DFXZA Ver. AA02 with the seemingly common power cycling problem

Any corner store should have small bottles of the lighter fluid for zippos.

I dont recall if they were in parallel but its entirely possible. At the time I didnt know what the component was so I had no idea if the shorted pins were just shared pins or if it was actually shorted. The Lighter fluid put that guess to rest and pointed out the exact component to pop off..
Oh, and I think someone pointed out, yes you can run without the diode and even without some of the caps. but its best to eval that on a case by case basis.

[nomoresonys]

Re: Samsung UN55KS800DFXZA Ver. AA02 with the seemingly common power cycling problem

Maybe also test those little ceramic capacitors. You can test them for shorts or low ohms, multimeter set to 200 ohms test probe on each side of cap, see if any read short or read very low ohms, I would be suspicious of any testing lower than about 100 ohms, most will probably read higher, often only one is bad but it will make several read bad, one technique is to remove one bad one at a time and check it again off the board and recheck any on the board that were reading bad, when you get the bad one off the others will read ok, if that is the problem.

[SoftwareHack]

Re: Samsung UN55KS800DFXZA Ver. AA02 with the seemingly common power cycling problem

Yeah, we're fast approaching the limits of my current skill and tool set. I'm pretty sure I can find the bad component(s), but I'll have to do some "learnin'" on removing and installing SMD's.

[SoftwareHack]

Re: Samsung UN55KS800DFXZA Ver. AA02 with the seemingly common power cycling problem

Okay...armed with only a multimeter mind you, I checked resistance of all of the resistors and they all match the value printed on top. One 100 ohm resistor read 62 ohms, but I checked it against the identical one on the board on the other and and got the same result. I'm assuming it has something to do with what they're connected to? I then checked continuity on each capacitor and found that only one side of each connected to ground. I assume this means no shorts. I also tested each for resistance, they all zero'd then started going up continuously. As I understand it, this is what is supposed to happen when good. Now I have to test the diode arrays. I tested them for shorts a couple of times with sewing needles in alligator clips at the end of my probes leads as my pin probes are way too large. I could get continuity between the grounds on each side of the chip so the setup was working. I didn't find any shorts this way. I have some needle point probe leads coming and I'll retest when I get them. Is there a chance that it's the LED's themselves that are bad and causing this problem? I can't see how to disassemble the panel to get at them just yet.

[Davi.p]

Re: Samsung UN55KS800DFXZA Ver. AA02 with the seemingly common power cycling problem

No led! The screen is lcd...if you don't find a short it means the short is not steady and so must use other method, i don't use it but the easiest is the Kilroy's liquid seems. Leave stay resistors, them can't go shorted.

[nomoresonys]

Re: Samsung UN55KS800DFXZA Ver. AA02 with the seemingly common power cycling problem

No led! The screen is lcd...if you don't find a short it means the short is not steady and so must use other method, i don't use it but the easiest is the Kilroy's liquid seems. Leave stay resistors, them can't go shorted.

??? The backlights are edge lit led.

[xfox]

Re: Samsung UN55KS800DFXZA Ver. AA02 with the seemingly common power cycling problem

Had 65 inch same model, same powercycle, check for bad ceramic caps on LCD boards, just switch multimeter to beep mode and go over bad side (I think you mentioned that one side is bad )

[SoftwareHack]

Re: Samsung UN55KS800DFXZA Ver. AA02 with the seemingly common power cycling problem

Had 65 inch same model, same powercycle, check for bad ceramic caps on LCD boards, just switch multimeter to beep mode and go over bad side (I think you mentioned that one side is bad )

Already did continuity check on all caps on the bad side, all passed (ie one side connected to ground and sounded, other side didn't sound at all). Also tried continuity check between each side of the caps, no sound on any.

[Davi.p]

Re: Samsung UN55KS800DFXZA Ver. AA02 with the seemingly common power cycling problem

sorry for many english errors, i'm curoius about the lighter filler method, can't you try please? Are you sure about model number? aren't there three zeros? Maybe UN55KS8000FXZA..

[SoftwareHack]

Re: Samsung UN55KS800DFXZA Ver. AA02 with the seemingly common power cycling problem

sorry for many english errors, i'm curoius about the lighter filler method, can't you try please? Are you sure about model number? aren't there three zeros? Maybe UN55KS8000FXZA..

I have to buy lighter fluid when I go into town tomorrow. I did a heat test with an infrared thermometer and didn't find any component that was much hotter than the rest, but I'll still try it.

Yes, the model number is correct. The only difference that I can tell is the 800D was purchased at warehouse stores like Costco, whereas 8000 are purchased at other big box stores. This is pretty common.

[Kilroy2k1]

Re: Samsung UN55KS800DFXZA Ver. AA02 with the seemingly common power cycling problem

If you have some very high percentage rubbing alcohol you can use that in place of the lighter fluid. It has to be 95% or better because water will conduct and fry bits. Only draw back is it evaporates faster.
I prefer lighter fluid, its safer due to the lower evaporation rate and it is non conductive.

[vinceroger69]

Re: Samsung UN55KS800DFXZA Ver. AA02 with the seemingly common power cycling problem

sorry for many english errors, i'm curoius about the lighter filler method, can't you try please? Are you sure about model number? aren't there three zeros? Maybe UN55KS8000FXZA..

sorins video shows the lighter fluid method about 30 mins into this iphone video he uses this trick on tv and laptop boards too.
https://www.youtube.com/watch?v=0MdUP54juKc&t=1965s

[SoftwareHack]

Re: Samsung UN55KS800DFXZA Ver. AA02 with the seemingly common power cycling problem

I checked that, but my rubbing alcohol isn't high enough. I also want to get a magnifying light so I can see what I'm doing so I head into town to buy supplies.

[Kilroy2k1]

Re: Samsung UN55KS800DFXZA Ver. AA02 with the seemingly common power cycling problem

Any update on the status?

[SoftwareHack]

Re: Samsung UN55KS800DFXZA Ver. AA02 with the seemingly common power cycling problem

I waited until the weekend when I received my needle point leads as well and a magnifying clip-on for my glasses. I checked for a short on every diode array several times and didn't find anything except what's circled in the picture, D0006 (what is that? Part # 1043F7H, 5 pins on one side, 4 on the others) where all of the 5 pins on the one side seemed to be shorted but I found the same chip on the opposite (good) buffer board and it did exactly the same thing.

I just picked up some Ronsonol fluid today and will be trying it, but I'm not all that confident as I had run several tests using an infrared thermometer and didn't find any hot spots. I compared the temps. with the corresponding temps. on the opposite buffer board and they were almost identical. But I will try the lighter fluid today. The question is, if I don't find anything, what next? Do I need to look at the other end of the buffer board cables on the LCD (or whatever they're connected to)?

[SoftwareHack]

Re: Samsung UN55KS800DFXZA Ver. AA02 with the seemingly common power cycling problem

So I tested it 3 times with the lighter fluid. I used a q-tip to spread it on a small section at a time, enough to surround each component as well as leave a "bubble" on top of them and let it cycle a few times. I did small section at a time so I wouldn't miss anything. I did not see any movement other than when it started to evaporate evenly across the test area. This confirms what I saw with the infrared thermometer, just a slow heating up of the board pretty evenly across all components, no hot spots.


BTW - D0006 also didn't show any movement.

Is there another level deeper to check? What is between the buffer boards and the LCD, if anything?