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

[SoftwareHack]

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

I'll look into that tomorrow.

[nomoresonys]

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

I'm gonna give the ice cubes a shot, Tried the canned air, not much luck, must be a certain technique and I don't have it. I wonder if anyone has tried dry ice, that shit is cold.

[diif]

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

The cheap canned air uses butane as a propellant, inverting the can causes the heavier liquid butane to come out first.
Maybe your air doesn't use propane, are you seeing frost on the nand when you do it ?

[SoftwareHack]

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

I just tested it against some glass and I get frost and it is wet to the touch when the frost disipates.

[nomoresonys]

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

This is the only time I wish it was below zero outside, for just an hour or two, would make it a lot easier.

[nomoresonys]

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

Youtube to the rescue, I remember hearing about or seeing this before, put a bit of that on your metal bar, maybe work quick so it doesn't get too cold, now to hunt down mine: https://www.youtube.com/watch?v=g8hJyR6P-qM

[nomoresonys]

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

One important thing he forgot to mention, DO NOT store in an airtight container, sublimation can cause it to explode, just need a little anyway, no need to store it actually, can burn like hell, adult supervision required.

[RJARRRPCGP]

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

2017

That's still more than late enough!

[Kilroy2k1]

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

I have this exact model and had the power cycling issue. Turned out to be a diode on the driver board.
With the TV laying on the bench with the back facing you you'll see theres 4 driver boards along the bottom.
The main board connects directly to the 2 center ones and there are small flex cables attaching the outer boards to the inner ones.
On the left hand one disconnect the flex between boards and then plug it in, see if it power cycles..
if it still cycles, reconnect and do the same to the right hand one.
Let me know if you get the back lights to stay on at all.
Tom.

[SoftwareHack]

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

I have this exact model and had the power cycling issue. Turned out to be a diode on the driver board.
With the TV laying on the bench with the back facing you you'll see theres 4 driver boards along the bottom.
The main board connects directly to the 2 center ones and there are small flex cables attaching the outer boards to the inner ones.
On the left hand one disconnect the flex between boards and then plug it in, see if it power cycles..
if it still cycles, reconnect and do the same to the right hand one.
Let me know if you get the back lights to stay on at all.
Tom.

I haven't taken it that far yet. I tested the power board connected to the main board and backlights with nothing attached to the main board and it continued to cycle so I didn't dig down deeper in my testing so far. I'm focusing on the main board at the moment, but I'll take a look at the drivers too. I also tested the power board connected to the mainboard with nothin else except the standby LED connected (even backlight disconnected) and I observed the cycling pattern on the standby LED.

[SoftwareHack]

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

Here's what I got when checking voltages on the power connector CNM803 on the power board to the main board. The odd thing is that in standby mode, I would get different values for Vamp and A13V when I ran it at different times. It's as if shutting it down by pulling the plug didn't reset it to standby, but it remained constant until I pressed the power button.

The 3 main checks were done in Standby (before pressing power button), Cycle On (when backlight flashed on briefly and sound was on for a second), Cycle Off (when backlight went back off and no sound was heard but not quite back in standby mode).

I ran the test 4-5 times with the same results except for what was noted above during Standby mode during different tests.

All cables connected in this test.

Thoughts?

[nomoresonys]

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

Are you sure about the last column OVD ON/OFF=19.6 VOLTS and BLU ON/OFF=50 VOLTS? And your getting 4.8 volts at BLU ON/OFF when it's on. I believe your fail count should be 0 if all is well, that looks off too, wonder if that's a backlight SOS? It doesn't seem like it should be tho, because your backlights stayed on with main to powerboard cable unplugged.

[SoftwareHack]

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

Are you sure about the last column OVD ON/OFF=19.6 VOLTS and BLU ON/OFF=50 VOLTS?

Yes, got the same numbers on at least 2 different runs.

When Cycle On BLU ON/OFF floated between 0 and 4.8, never stopping on one value.

Also, the PWM numbers 1.2/2.4 means it was 1.2 when backlight flashed on and of 2.4 when sound could be heard briefly and 0.36 when it cycled off (no backlight, no sound, standby light goes on for a few seconds).

When in standby mode (before I ever push the power button) I can hear an audible clicking on the main board for 2-3 seconds that cycles periodically but nothing else lights up until I press the power button.

[SoftwareHack]

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

i ran tests again on OVD On/Off and BLU On/Off and here's the consistent results: (backlight goes on for a second or so, same with the sound)

---------------Standby--Clicking--Backlight On--Sound--Back to Standby
OVD On/Off--20.0------floating--3.3-------------0.6-----20.0
BLU On/Off---50.0------floating--0.0-4.8--------4.2-----50.0

[budm]

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

Are you sure the 20 and the 50 readings are not in mV?
They cannot be 20V or 50V since the logic circuit does not run on that high of the Voltage.

[SoftwareHack]

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

You are correct. My meter is not illuminated and I did not see it switch to mV on the fly, so those are mV numbers.

[Davi.p]

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

Can you point out which is precisely the behaviour of the TV? If you see no images at all consider that mainboard is all in one with tcon, the tcon is a common source of problems in theese very fragile boards, often there is a "dirty" tiny cap in crisis that keeps in mad chess an entire 1000$ TV and carries it along the way of landfill like a Doctor House unknown parasite... check well Youtube videos of Adamant IT, it reveals the mother of techniques of fault findings, i use a slighty different method but it doesn't matter.. i follow the one from my experience but maybe them are swappable..

[SoftwareHack]

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

Upon plugging in the power, standby LED illuminates, but nothing else comes on. Pressing the on/off button, no picture at all, a bit of a delay, then backlight flashes on for a second then off, then sound comes on for a second then off, and then the TV goes into standby (or seemingly standby) for another 12 seconds then the cycle starts up again. Image never comes on.

This mainboard does have a built-in TCON. I have not looked too carefully at the main board other than to try and spot burnt components or broken solder joints but didn't find anything. Also did a continuity check on the cable to the power board to see if there was a short in the cable. All wires continuous and none shorted to adjacent wires (of course it would never be such a cheap problem). I'm hoping to avoid doing much on the main board as I'm just a software hack (see my name) and my hardware skills light at best...

Backlight will come on and stay on only under the condition that the connector to the mainboard is disconnected. Power cycling happens even when only the power board is connected to the main board and the standby LED is connected (to visibly verify the cycling). So I don't think the panel is responsible for this particular issue.

[Davi.p]

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

If you are not expert enough, better to search for a mainboard.. if it doesn't work sell tv for entire as faulty.

[SoftwareHack]

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

I don't expect to be able to repair the main board myself. Just hoping to isolate the issue and buy the right replacement. Main boards for this model runs from $50-$230 with the lower prices coming from individuals with no background in repair so I don't even consider those. Shopjimmy.com is out of stock on boards for this model.

I'm hoping it's just a corrupt flash issue that can be corrected by an update, but I have to get beyond this cycling problem to update.

But yes, if it's not a simple fix, then I will be looking for a new main board.