Samsung UE55JU6872UXXH - Lower third darker

[bbccbb]

Hello...
I have a problem with Samsung UE55JU6872UXXH.
Lower third of the screen is darker than the upper two thirds.
Is this a LED problem or LCD panel problem?
Two photos attached.

[Diah]

Re: Samsung UE55JU6872UXXH - Lower third darker

to me its hard to say the reason, unless if you show us clear photo of your PSU and the LED back light socket. also some reading on it with DM

[CapLeaker]

Re: Samsung UE55JU6872UXXH - Lower third darker

measure the voltages on each LED string.

[bbccbb]

Re: Samsung UE55JU6872UXXH - Lower third darker

This is it for today.
I'll do all the rest on Sunday. I hope.
And report back.

[R_J]

Re: Samsung UE55JU6872UXXH - Lower third darker

My guess would be bad led's (shopjimmy is out of them) Looking at the power supply board, there are two seperate strings for the backlights and there are LED Test points marked on the board near the CNL802 connector
the voltages are different for each line. [2D] CH1 227v @500ma CH2 182v @500ma [3D] CH1 267v @1amp & CH2 250v @1amp

[bbccbb]

Re: Samsung UE55JU6872UXXH - Lower third darker

My guess would be bad led's (shopjimmy is out of them) Looking at the power supply board, there are two seperate strings for the backlights and there are LED Test points marked on the board near the CNL802 connector
the voltages are different for each line. [2D] CH1 227v @500ma CH2 182v @500ma [3D] CH1 267v @1amp & CH2 250v @1amp

I thought that PSU would shut down the whole backlight if the LEDs are bad. That happened to my old Sharp TV. I replaced the faulty LED and it worked. Until I applied force while closing the frame. And broke the LCD panel.

So, you're saying that PSU is driving two parts of the backlight... and lower part is faulty somewhere...

Thank you for the pointers!

But I'll be able to test that on Sunday.

[budm]

Re: Samsung UE55JU6872UXXH - Lower third darker

What is the power supply board P/N? BN44-?????
This one?
https://www.shopjimmy.com/samsung-bn...-led-board.htm
Also need to provide good clear pictures of the whole backside of the TV showing all the boards.

[bbccbb]

Re: Samsung UE55JU6872UXXH - Lower third darker

Ok... I've managed to make photos.
Power supply has alot of dust on capacitors and wires.

[nomoresonys]

Re: Samsung UE55JU6872UXXH - Lower third darker

So blow off the dust and report the voltages as suggested.

[bbccbb]

Re: Samsung UE55JU6872UXXH - Lower third darker

My guess would be bad led's (shopjimmy is out of them) Looking at the power supply board, there are two seperate strings for the backlights and there are LED Test points marked on the board near the CNL802 connector
the voltages are different for each line. [2D] CH1 227v @500ma CH2 182v @500ma [3D] CH1 267v @1amp & CH2 250v @1amp

Near CHL802 are two resistors marked with LED TP, but when I measure voltage on these resistors I get 0V. I've measured by putting probes on ends indicated by arrows.

Should I try to measure voltage on the connector? It has 4 wires, one marked with black and three gray ones.

[bbccbb]

Re: Samsung UE55JU6872UXXH - Lower third darker

What is the power supply board P/N? BN44-????

Power supply has this on it:
L55SHN_FHS BN44-00859A

[bbccbb]

Re: Samsung UE55JU6872UXXH - Lower third darker

I've measured voltages against chasis on both resistors.
Upper resistor has 160-190V.
Lower resistor has 40-60V.
Voltages varry on colour.

[bbccbb]

Re: Samsung UE55JU6872UXXH - Lower third darker

My guess would be bad led's (shopjimmy is out of them)

Is there a way to know which strips do I need for my TV without getting to the basklights and looking at them?

Shopjimmy has two:
Samsung BN96-38880A/BN96-38881A Replacement LED Backlight Strips (18)
Samsung BN96-38481A/BN96-38482A LED Backlight Strips (18)

I suppose it would be best to replace them all and not try to find faulty one, right?

[bbccbb]

Re: Samsung UE55JU6872UXXH - Lower third darker

I got to the back lights... and this is how LEDs look like.
Now I have to remove the white plastic and test LED strips.

[bbccbb]

Re: Samsung UE55JU6872UXXH - Lower third darker

How to remove this white spacer? It holds reflective sheet... and back part is behind power board and other one is behind main board.

[R_J]

Re: Samsung UE55JU6872UXXH - Lower third darker

Look at the back of the panel where they stick through, but I believe you give them a half turn and the pull out oR you lift the bottom edge (pin) and they slide down

[bbccbb]

Re: Samsung UE55JU6872UXXH - Lower third darker

I'll have to remove power board or main board to look at the other end of the spacer...

[R_J]

Re: Samsung UE55JU6872UXXH - Lower third darker

There are spacers all over the panel. can't you see any of them from the rear? It is possible there are clips that need to be compressed from the rear to remove them but I'm sure I have removed them from the front before without a problem.

[bbccbb]

Re: Samsung UE55JU6872UXXH - Lower third darker

This kind is special.
Other ones have the cros cut around them and I do not think I have to pull them out. Only these few that are white.
And I can see others at the back... and I think that they cannot be removed.
I'll make some photos.

[budm]

Re: Samsung UE55JU6872UXXH - Lower third darker

Those standoff I turn it 90 degree and pull out.