Samsung UE40F6340 turns off automatically

[Steradiant]

My Samsung UE40F6340, which I only use occasionally, has recently started turning itself off. It can take a few seconds to a few minutes before it happens. I've checked the auto sleep settings and similar options and found that none of them are enabled. I also unplugged all connected devices, but that didn't change anything. Of course, I also tried a different power outlet, which didn't help either.
After that, I opened the TV to see if there was any apparent defect, but found nothing. Pictures are attached. Then I disconnected the cable between the power board (right side) and the receiver board (left side). When I did that, the TV didn't turn off. So I assume that the receiver board is sending the shutdown signal.
Do you have any ideas what could be causing this?

[lotas]

The main problem with this chassis is the eMMC.

[Steradiant]

Is there a way to confirm that this is the problem? I guess nothing else than replacing the entire board would (possibly) solve the issue?

[Diah]

try freeze eMMC, put the set in STBY, then call service menu.. from there do Factory reset.. just try to keep it under freezing during yours work. hope it will correct dead sector

[lotas]

Well, if you don't have a programmer for eMMC and you don't know how to transfer native keys to a new eMMC programmed with a working dump, then yes, only a motherboard replacement. For diagnostics, try heating it up a little with a hair dryer at 100 degrees Celsius.

[nomoresonys]

So do you freeze it or heat it?

[nomoresonys]

I think the odds of either working are pretty low.

[lotas]

It might work for diagnostics, but for full operation I still need to change it to a new one.

[Steradiant]

So, how sure are you, without any tests, that it is the eMMC and a change of the receiver board would solve the issue? How big are the odds that the power supply board has an issue and there is a voltage drop that causes the main board to send the "switch off" command?

try freeze eMMC, put the set in STBY, then call service menu.. from there do Factory reset.. just try to keep it under freezing during yours work. hope it will correct dead sector

So, just to be clear, you actually mean freezing as in lowering the temperature, like putting it in the freezer? Sounds tricky to do this while simultaneously doing a factory reset.

Well, if you don't have a programmer for eMMC and you don't know how to transfer native keys to a new eMMC programmed with a working dump, then yes, only a motherboard replacement. For diagnostics, try heating it up a little with a hair dryer at 100 degrees Celsius.

What is the expected outcome when I heat it up? Do I do this while it is running?

Would it even be possible to easily replace the eMMC? Isn't that soldered in?

If I'm exchanging the entire board, how closely do the board numbers have to match? I found one from an UE46F5570, which looks similar but not entirely the same. Mine has more USB and HDMI connectors.

[bohaboha]

So, how sure are you, without any tests, that it is the eMMC and a change of the receiver board would solve the issue? How big are the odds that the power supply board has an issue and there is a voltage drop that causes the main board to send the "switch off" command?



So, just to be clear, you actually mean freezing as in lowering the temperature, like putting it in the freezer? Sounds tricky to do this while simultaneously doing a factory reset.




What is the expected outcome when I heat it up? Do I do this while it is running?

Would it even be possible to easily replace the eMMC? Isn't that soldered in?

If I'm exchanging the entire board, how closely do the board numbers have to match? I found one from an UE46F5570, which looks similar but not entirely the same. Mine has more USB and HDMI connectors.

My friend use a can to freeze ii wile you are testing for Diah suggestion.
and the hair dryer for lotas while you test

[Diah]

So, just to be clear, you actually mean freezing as in lowering the temperature, like putting it in the freezer? Sounds tricky to do this while simultaneously doing a factory reset.

who talked on freezer lol... you never have under hand or see cool air can?

[Steradiant]

Obviously, I should change the temperature of the eMMC while running. I hadn't considered using compressed air for that, since it only seems to cause a small temperature change. Still, I'll give it a try.

However, I still have the following question: what is the expected behavior after I do this? And do I get it correctly, that I should cool the eMMC by compressed air and then switch it on and reset the TV?
And how sure are you, that it is the eMMC rather than the power board?

[Steradiant]

try freeze eMMC, put the set in STBY, then call service menu.. from there do Factory reset.. just try to keep it under freezing during yours work. hope it will correct dead sector

My friend use a can to freeze ii wile you are testing for Diah suggestion.
and the hair dryer for lotas while you test

I tried this today, but it did not help. However, I measured the voltages on the CNM803 while the TV was on.

Here are the values:


And what the board says:


My multimeter did not output a value for 10 ECO_ON/OFF, so I put the dash there. For the PWM signals, I only measured the DC value with the multimeter since I did not have an oscilloscope at hand. The only values that surprise me a little bit are the B13V values for pin 7 and 9 since they are comparably low with 12.3V. Could that be an issue?

Are there any other test I can make to confirm if either the mainboard or the power supply board are causing the problems?

[nomoresonys]

So youre saying with mainboard unhooked from powerboard you have backlights on and steady, if so that should eliminate backlights and powerbard from fault. That leaves mainboard or panel or a cable in between that is the issue. Maybe check the voltage of the little mlc caps near the emmc chip.

[nomoresonys]

You have a survivor from circa 2013 there so prolly is bad emmc or processor but if it was used very seldom I would think the emmc should be alright.

[nomoresonys]

Maybe try unhook mainboard from tcon or driver board depending on your setup and turn tv on, see if it stays on, will be no display of course.

[nomoresonys]

It always helps if you post a good picture of the entire back so as to see what it is and how everything is connected.

[Steradiant]

So youre saying with mainboard unhooked from powerboard you have backlights on and steady, if so that should eliminate backlights and powerbard from fault. That leaves mainboard or panel or a cable in between that is the issue. Maybe check the voltage of the little mlc caps near the emmc chip.

Yes, this is the case. However, what if a voltage drops on the power board and the main board recognizes that corretly and sends the turn off signal. Wouldn't that be possible too?

Maybe try unhook mainboard from tcon or driver board depending on your setup and turn tv on, see if it stays on, will be no display of course.

I did this already. The issue persists, meaning the TV turns off (goes to standby) after a approximately a minute.

[nomoresonys]

That test with mainboard unhooked and backlights are on and steady is pretty much a constant and indicates that backlights and powerboard are ok. My guess is mainboard issue, mainboards issues are not easy to deal with even for the pros. Being 40 inches, you might be able to find one for a decent price, if not looks like time to recycle. You can try cleaning the cable ends with a pencil eraser just in case but most likely mainboard is the problem.