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

[Kilroy2k1]

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

Burn that bridge when you get to it. No point in asking whats after the next step when you havent done the next step.
Dab the fluid on the components a small section at a time and watch the area closely while it power cycles.

[SoftwareHack]

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

This is what I did. About an inch at a time. I even shined an LED light array on the area to illuminate the fluid while viewing through a 8x magnifier. Zilch. I did each area multiple times to make sure I didn't miss anything, letting it cycle several times while viewing each section.

BTW - I also tried swapping the linker cables with the one from the good side. No change, but it was worth a shot.

[nomoresonys]

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

.

[nomoresonys]

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

Well haven't tried the " tape cut-off" method.

[nomoresonys]

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

This video gives a pretty good explanation of his problem and fix: https://www.youtube.com/watch?v=pfrRhw7-ZII

[SoftwareHack]

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

Okay, I retested but I waited several minutes to allow everything to warm up a bit more than the first time I tested it. This time, I did see the "heartbeat" on D005. And a much shallower "heartbeat" on R043 and R044. (See attachment. These are the same was what Nick's TV posted.

Now, what to do about it? I'd imagine that I can remove these components with my small Weller soldering iron, but I don't have replacement parts. I'd imagine the resistors would be fairly easy to come by online, but I couldn't find a replacement for the diode array (4265H). Is it true that I can simply remove these parts? Is the diode array just there for ESD protection (just from my looking up what they might be used for)? And the resistors?

TIA

[nomoresonys]

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

Maybe track it out to the tcon ribbons and block that signal with tape.

[SoftwareHack]

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

This video gives a pretty good explanation of his problem and fix: https://www.youtube.com/watch?v=pfrRhw7-ZII

Unfortunately, I don't see any indication of the clock lines on the boards on either end of the ribbon cables. Pretty cool trick though.

[nomoresonys]

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

Well maybe you can replace that diode array, it did test bad right?

[SoftwareHack]

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

With the lighter fluid test, I did see the liquid heartbeat, but only after I let it warm up several minutes before testing. The resistors also showed a much shallower heartbeat.

The diode array has a part number: 1043F7H that can't find with just a Google search. The resistors are marked 51R0 which I understand are 51.0 ohm. I figure that the resistors wouldn't be hard to find.

[Kilroy2k1]

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

Ignore the resistors for the moment, they are likely getting hot due to the diode.
yes you should be able to remove that diode safely and test the tv.
With your pencil iron get an overabundance of solder on it and it'll come off with the added thermal mass of the extra solder.

[SoftwareHack]

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

Thanks. I'll give it a shot.

[Kilroy2k1]

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

And if you really want to change it, here is some info on the diode array.

[SoftwareHack]

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

Thanks. I would like to replace it, eventually, but I may need better tools to install it. My soldering iron has a pretty wide tip. I may have to go into town tomorrow to see if I can find a small tip for it.

[Kilroy2k1]

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

Wide tip is better for removal, make sure the tip is clean and use a fair bit of flux, get it in there on one side of the chip, preferably away from the flex cable, cover as many of those visible solder pads (the 5 connections on one side of the chip i called pins before) as you can and then feed it extra solder and flux, when its to temp it'll just slide off like nothing. Dont rush it, dont push hard, let the heat do its thing.

[SoftwareHack]

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

Is the flux necessary? I have a small container of it, but I cannot find it. Can I just use flux core solder?

The chip that needs removal is D005, near the end of the board so no flex cable to worry about.

[Kilroy2k1]

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

The flux would help but you can do without.
Theres a flex cable 1/2" away from the diode, just dont flick the hot diode on to it.

[SoftwareHack]

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

I see see what you're saying...the flex cable to the panel. I'll tape a little shield in front of it because you never know. I'm going to hold off until tomorrow and get some flux and desoldering wick. I don't want to mess this up now...I'll report the results tomorrow.

[Davi.p]

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

Those diodes are almost probably tvs diodes and are there for overvoltage suppression, must be replaced if without it works, one side, anode is tied to ground and this why you read short, your problem is on the VGHD signal , a gate driver biasing tension, can you make me a test please? I'm curiuos on how the termal camera works, i don't knew you had if yes i would not suggested you the liquid... can you watch with camera the bad part waiting the same minutes as the fluid and see if a problem spot is visible?

[SoftwareHack]

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

Those diodes are almost probably tvs diodes and are there for overvoltage suppression, must be replaced if without it works, one side, anode is tied to ground and this why you read short, your problem is on the VGHD signal , a gate driver biasing tension, can you make me a test please? I'm curiuos on how the termal camera works, i don't knew you had if yes i would not suggested you the liquid... can you watch with camera the bad part waiting the same minutes as the fluid and see if a problem spot is visible?

I do not have a thermal camera so I used the lighter fluid check to find the offending chip.

Now, my first attempt at removal is a failure. I got some flux and applied it with a toothpick, all pads covered. However, when I went to apply the solder, I could not get in tight enough to get the solder to the pads. The soldering iron tip is too wide. This chip is tiny. What are my options? Would the easiest thing to get a low end hot air reworks station? Or a sharper tip for my soldering iron?