Samsung UN46F6300 - Powers Off Shortly After Power On - Not in On/Off Loop

[monte1967]

I have a Samsung UN46F6300AFXZA LED SmartTV (manufactured in Jan 2014) that began intermittently turning off several months ago. It got progressively worse and is now to the point where it turns off every 2-3 minutes. It powers down and is not in an on/off power cycle loop. Firmware is .2011 and the latest is .2025. I cannot get the TV to stay on long enough to attempt a firmware update, nor do I think it is the problem. I have performed multiple factory resets, made sure all AnyNet/CEC features are turned off and all ECO settings and loss of signal power down options are turned off. I have inspected the caps on the power supply board and all are good. I replaced the power supply board because it was cheap and the problem persists. I have checked all connections and inspected all boards for obvious defects. Any thoughts on this one? I have a DVOM and would considered myself somewhat skilled at performing tests, but I do not know enough to start testing without some direction or a troubleshooting guide. Any help would be appreciated. Thanks!

[nomoresonys]

Re: Samsung UN46F6300 - Powers Off Shortly After Power On - Not in On/Off Loop

Try unplugging the cable from powerboard to mainboard, then turn tv on see if your backlights come on and stay on.

[monte1967]

Re: Samsung UN46F6300 - Powers Off Shortly After Power On - Not in On/Off Loop

I unplugged the ribbon cable from the main board to the power board and then plugged the TV in. The back lights came on immediately and stayed on. I let it go for ten minutes and then unplugged it. I am guessing this little trick would have proved my original power board was okay and saved me two weeks of waiting on a new board (first one came damaged by USPS).

[nomoresonys]

Re: Samsung UN46F6300 - Powers Off Shortly After Power On - Not in On/Off Loop

Ok, try testing pin 6 BLU, on connector CNM803, test with all boards hooked up, test with tv plugged in but not on which is standby take note, then hit power on and see what you get, thinking you are not getting the backlight on signal from mainboard.

[nomoresonys]

Re: Samsung UN46F6300 - Powers Off Shortly After Power On - Not in On/Off Loop

Example of how to test powerboard. https://www.youtube.com/watch?v=4v8DcqCNG4A

[monte1967]

Re: Samsung UN46F6300 - Powers Off Shortly After Power On - Not in On/Off Loop

Readings from pin 6 on connector CNM803 as follows -

TV Off but plugged in - 0.00 VDC
Initial power button press - 0.15 jumps to 0.91 VDC
Less than a second after power button press - 4.82 VDC (to either pin 8 or pin 10 GND or chassis)
When TV appears to shut off - 0.00 VDC

Although the red power indicator stays on, I noticed that a small blue LED on what I believe is the video driver board also goes out when I lose the back light signal. Seems like the main board is what is flaking out?

[nomoresonys]

Re: Samsung UN46F6300 - Powers Off Shortly After Power On - Not in On/Off Loop

Ok, that's good, at least you are getting the backlight on signal from mainboard, could be something else wrong with mainboard tho.

[nomoresonys]

Re: Samsung UN46F6300 - Powers Off Shortly After Power On - Not in On/Off Loop

Most of the time, when you have it going off after say an hour then maybe after a month or a week starts going off in 10 minutes, could be one or more bad capacitors on the power board, they don't have to bulge to be bad, they can be tested if your multimeter has a capacitance mode. Suppose this could be the case if you have a bad capacitor on the replacement board.

[nomoresonys]

Re: Samsung UN46F6300 - Powers Off Shortly After Power On - Not in On/Off Loop

This worked for someone BUT their tv was turning on and off.
Turning off the internet on the TV stopped the TV from turning off. (We had just about a minute to do this before it would turn off again.) I had to turn it off from the menu, network, network status. -- Internet Connections. Not sure of the exact words. I just disabled the internet from the TV menu

I went to my computer and entered: Samsung Update and the Model No - get the latest update.

I downloaded the latest update on a USB then put it on the TV (When our TV internet was on it would not update from the USB - It seems it's trying to update from the internet and keeps resetting) We tried several times and then when we we turned off the Internet connection on the TV, it downloaded the update without interruption. It worked and the TV is not dysfunctioning anymore.

STEPS WE TOOK - When we had the update on the USB and the Internet is disabled on the TV, I Inserted the Updated USB then I went to the Menu, then: Support, then: Software Update: Then Update Now

[monte1967]

Re: Samsung UN46F6300 - Powers Off Shortly After Power On - Not in On/Off Loop

I have tried resetting the TV several times and disabling the network connection on startup. I have also accessed the factory service and diagnostic menu and tried figuring out a way to update the firmware from there. The TV just shuts off so fast that I cannot do anything. The software update menu is always grayed out which is a bit odd. Either way it sounds like it is a main board and I am struggling to find one, or one at a decent price. I really hate to replace the TV when it is only four years old. Ugh...

[nomoresonys]

Re: Samsung UN46F6300 - Powers Off Shortly After Power On - Not in On/Off Loop

Could try unplug wifi wireless module, see if anything changes, should look something like this: https://www.shopjimmy.com/samsung-bn...-fi-module.htm

[nomoresonys]

Re: Samsung UN46F6300 - Powers Off Shortly After Power On - Not in On/Off Loop

Think I would try a new eeprom, looked a bit on the net but I couldn't locate any.

[monte1967]

Re: Samsung UN46F6300 - Powers Off Shortly After Power On - Not in On/Off Loop

I found a main board for $60. I received it yesterday and quickly installed it. Everything worked great. I went to put the old board in a box today and noticed something I forgot....some sort of heatsink pad attached to the back of the board behind the processor that appears to be there to dissipate heat into the metal frame of the TV. I pulled the main board back off and put it in the marked area. When I went to screw down the main board I noticed the board bulging up. This heatsink pad appears to be made about 1/8 inch too wide and it won't fit between the ribs of the metal frame. I trimmed it off with a razor blade and reinstalled with direct contact between the metal frame and the main board, but no bulging. I wonder if this pressure on the board through heat up and cool down cycles is causing a solder joint on the processor to fail? I thought it was an interesting find. Either way the TV is fixed and has been working all day with no issues. Thanks for all of the help!

[nomoresonys]

Re: Samsung UN46F6300 - Powers Off Shortly After Power On - Not in On/Off Loop

Nice, glad to hear it, thanks for the followup.