Samsung UN65NU6900FXZA Stand-by light on but voltages on PS indicate TV should be on

[DXseekerMO]

Hello everyone!

Tonight I picked up a Samsung UN65NU6900FXZA with a curious issue.

Symptoms:

1) Plug TV in to AC outlet, stand-by light illuminates briefly and goes out.
2) TV does not appear to turn on
3) Backlights do not illuminate, voltages associated with backlights on Power Supply are not present
4) "Power on" terminal on Power Supply has 3.26v
5) "A13V" terminals have 12.9v
6) Stand-by test jumper on Power Supply has 12.9V
7) Optical audio jack on Main Board illuminates
8) With stand-by light off a pulse is seen on the stand-by light when the "POWER" button is pressed on the remote but the TV fails to respond.
9) A couple minutes after plugging TV in to AC outlet stand-by light turns back on, and does so on it's own
10) With stand-by light on "Power on" terminal continues to have 3.26v
11) With stand-by light on "A13V" terminals continue to have 12.9v
12) With stand-by light on stand-by test jumper terminal continues to have 12.9v
13) With stand-by light on optical audio jack on Main Board continues to illuminate.
14) With stand-by light on a pulse is seen on the stand-by light when the "POWER" button is pressed on the remote, returns to solid illumination when the button is released and the TV does not turn on.
15) If the TV is unplugged from AC power and plugged back in all of the above repeat.
16) There is no change in symptoms with either or both LVDS cables detached from Main Board
17) When main board connector is disconnected from the Power Supply the backlights illuminate and all the prescribed voltages are present.

This appears to be a Main Board issue. Does anyone concur?

I've found several Main Boards under $30.00 so I don't plan on troubleshooting it to component level, but I would perform other testing to confirm if needed.

[dick_barton]

Re: Samsung UN65NU6900FXZA Stand-by light on but voltages on PS indicate TV should be

So the "Power On" signal does not toggle state when you press the remote to turn on the set. If not then it would appear to be a mainboard issue.

[DXseekerMO]

Re: Samsung UN65NU6900FXZA Stand-by light on but voltages on PS indicate TV should be

So the "Power On" signal does not toggle state when you press the remote to turn on the set. If not then it would appear to be a mainboard issue.

That is correct, and the stand-by voltage never toggles between 7 and 13v.

[DXseekerMO]

Re: Samsung UN65NU6900FXZA Stand-by light on but voltages on PS indicate TV should be

This TV has Main Board part# BN94-12873M. I just checked my parts stock and I have a Main Board part# BN94-12873C for the same model, just a different version. There is a slight variance in the panel part numbers between the 2 TVs.

I wonder if it would hurt anything to use the C suffix Main Board to test the rest of the TV? I know this model is having panel issues and it would be nice to verify the panel works before ordering a Main for this.

Does anyone have an opinion about substituting the C suffix board temporarily, and for testing purposes only?

[DXseekerMO]

Re: Samsung UN65NU6900FXZA Stand-by light on but voltages on PS indicate TV should be

Ok so I decided to install the 12873C board but DID NOT attach the LVDS cables to it.

The stand-by light illuminated, and when I pressed the power button the TV turned on, the backlights came on full brightness, dimmed, came back up to full brightness and I got an audio prompt for TV set-up. I pressed the power button and the TV turned off normally.

Now begs the question....do I dare hook the LVDS cables up to the Main Board?

The previous owner said the TV was working normally when they turned it off and went to bed. The next morning they tried to turn it on and it presented with the symptoms I mentioned in the first post.

I'm not so sure it's worth the risk to the screen or Main Board to attach the LVDS cables. I can't see the TV working fine with a good picture and the screen being short the next morning....although stranger things have happened.

SO what do we think here folks....hook them up or just get a Main Board coming?

[ikmpch]

Re: Samsung UN65NU6900FXZA Stand-by light on but voltages on PS indicate TV should be

Check the 12VDc supply on LVDS connector on main board. If present, it should be good to connect.

[DXseekerMO]

Re: Samsung UN65NU6900FXZA Stand-by light on but voltages on PS indicate TV should be

Check the 12VDc supply on LVDS connector on main board. If present, it should be good to connect.

Thanks for the reply on that ikmpch. I have a Main Board coming from New York so I think I will go ahead and wait until it gets here.

[DXseekerMO]

Re: Samsung UN65NU6900FXZA Stand-by light on but voltages on PS indicate TV should be

So the "Power On" signal does not toggle state when you press the remote to turn on the set. If not then it would appear to be a mainboard issue.

Check the 12VDc supply on LVDS connector on main board. If present, it should be good to connect.

So the Main Board came in today. I installed it and the TV is now working great! The picture looks as good as it can for this model and there's no backlight/main diffuser issues far as I can tell.

Thanks for everyone's input, I appreciate it!

[DXseekerMO]

Re: Samsung UN65NU6900FXZA Stand-by light on but voltages on PS indicate TV should be

Three days later and this TV is aces!