Samsung UA60D8000 Cycling On/OFF

[PHELLY]

Hi, I have a Samsung UA60D8000 which cycles on and off, there isn't enough time to carry out any measurements. I disconnected all cables from the power supply and I can measure the 12v and 5v rails. disconnecting the led strips only will not stabilise the supply but disconnecting the main board does but of course will not light the led strips as the TV cannot be switched on.
I am unsure whether the main board if faulty as I cannot see the supply running fully with the main board plugged in.
Does anyone know how the supply is activated by the main board and what pins are used or does this sound like a main board problem as I suspect.
I believe I have ruled out the LED strips by disconnecting them and the supply still cycles on and off.
Incidentally, for the second the set remains on, the Samsung logo is clear and bright.

[mmartell]

Re: Samsung UA60D8000 Cycling On/OFF

With the leds disconnected the power supply will likely go into protection so that test won't tell you anything.

Take a careful look at the screen when it lights for even lighting. Could be a bad strip or two which shuts the ps off shortly after power on.

Also hit the main board with a hair dryer. May have dodgy bga/solder connections.

[thoma]

Re: Samsung UA60D8000 Cycling On/OFF



ftp://helpedia.com/pub/temp/datashee...itors/Samsung/

may be help!

regards thoma!

[budm]

Re: Samsung UA60D8000 Cycling On/OFF

How about pictures of the whole back side of the TV so we can see how all the boards are connected together?
What happen if you disconnect the cable between the main board and the power supply, the backlights should come on and stay on when you plug the TV into the outlet (no need to hit the power switch).
What is the power supply board P/N? BN44-?????

[PHELLY]

Re: Samsung UA60D8000 Cycling On/OFF

Thanks for the Reply guys, I will also look at those links.
Unfortunately I cannot see if the led strips are fully lit as it only displays the Samsung logo for a second in the centre of the screen, not enough time or screen to see if the strips are failing.
I have tried unplugging the led strips but it still cycles, it is only when I disconnect the main board that it doesn't cycle.
I also believe that the leds will not alight unless the main board is connected as the power supply would require a feedback from the main board.
When the main board is disconnected the supply does not cycle, but obviously apart from the 12v and 5 volt rails to the main board the supply will not start, I believe that when the main board is connected and the supply is fully enabled it goes into protection for a second before restarting and again going to protection, so the cycle continues.

[retiredcaps]

Re: Samsung UA60D8000 Cycling On/OFF

Unfortunately I cannot see if the led strips are fully lit as it only displays the Samsung logo for a second in the centre of the screen, not enough time or screen to see if the strips are failing.

Take a video of the above and then play it back frame by frame using software like vlc.

[CapLeaker]

Re: Samsung UA60D8000 Cycling On/OFF

[QUOTE=PHELLY;601878]I also believe that the leds will not alight unless the main board is connected as the power supply would require a feedback from the main board.
QUOTE]

... unless the main board has a pull up resistor, which this D series should have. So do they light up with the main board disconnected or not?

[PHELLY]

Re: Samsung UA60D8000 Cycling On/OFF

Just a quick note, unplugging CN201 and repowering the TV does did not switch on the backlight. I followed the "Forced Backlight-on Mode" procedure.
I guess that indicates a power supply fault?

[CapLeaker]

Re: Samsung UA60D8000 Cycling On/OFF

yes

[PHELLY]

Re: Samsung UA60D8000 Cycling On/OFF

Thanks CapLeaker, and thanks for everyone else as well, I appreciate your help.

[budm]

Re: Samsung UA60D8000 Cycling On/OFF

So what is the Power supply/LED Driver board P/N? BN44-??????
We need to check the Voltages on the board.
Since the board is cycling we need to find out if the PS-ON is cycling ON and OFF or not.

[PHELLY]

Re: Samsung UA60D8000 Cycling On/OFF

Hi budm, The Code is BN44-00429a

[budm]

Re: Samsung UA60D8000 Cycling On/OFF

OK, shopjimmy does not have picture for the BN44-00429a, what I need is the Voltage readings on the white connector of the power supply board that goes to the main board, if you look closely you will see the chart printed on the board that tells you what each pin is for.
Can you take good closed up picture around that connector area so we can see what each pin is?
This board is not cheap.

[PHELLY]

Re: Samsung UA60D8000 Cycling On/OFF

I took a few shots, this one seems to be the clearest

[budm]

Re: Samsung UA60D8000 Cycling On/OFF

OK, pin 20 PS looks to be the PS-ON pin, pin 12 BLU is the BL-ON pin, and pin 18 is the Standby 5V.
So if the main board is not connected, then you should have steady DCV at pin 20 and pin 12, they should be >2VDC with ref to GND.
Then connect the main board cable back in place and check the Standby 5V, the PS PIN, and the BLU pin to see what is going up and down in sync withe on/off cycle.
BTW, what was the history of this TV? It just went out by itself and start clicking on and off.

[PHELLY]

Re: Samsung UA60D8000 Cycling On/OFF

So without the Main Board plugged in, pin 20 sits at 4.1v pin 12 at 2.9v, with the main board plugged in, stby is steady at 5v, pin 20 varies from 3.3 to 0v and blue pin varies but too quickly for my Fluke to read, drops to 0 and rises but instantly drops.

[PHELLY]

Re: Samsung UA60D8000 Cycling On/OFF

meant to add, I am unsure of how the set stopped whether it was while watching or while on standby, I can find out if it is important

[thoma]

Re: Samsung UA60D8000 Cycling On/OFF



ftp://helpedia.com/pub/temp/datashee...itors/Samsung/

[PHELLY]

Re: Samsung UA60D8000 Cycling On/OFF

Thanks Thoma, great information

[budm]

Re: Samsung UA60D8000 Cycling On/OFF

'So without the Main Board plugged in, pin 20 sits at 4.1v pin 12 at 2.9v' That is what I expect due to the fact that the pull-up resistors are built-into the power supply board.

'with the main board plugged in, stby is steady at 5v, pin 20 varies from 3.3 to 0v and blue pin varies but too quickly for my Fluke to read, drops to 0 and rises but instantly drops.' That means the main board is sending the command signal PS-ON is going up and down instead of steady state ON when TV is ON, this will cause the switched power supplies section to be tuning on and OFF. So you have main board problem not sending the proper PS-ON, and the Power supply/LED driver combo board that is not lighting up the backlights LED when the cable between the power supply and the main board is disconnected (it can be the LED driver circiut, the PFC not working, or bad LEDs).