Dismantling Samsung 55 LCD LED Screens

[Ltank]

Hi Guys,
I learned alot about the troubleshooting of the Samsung LCD LED TV.
I am at the point of taking apart the screen. I have the screen out of the set, boards are removed. All the small screws that hold the outer frame to the main backbone thatthe boards were mounted to have been removed. There is a white plastic section that sorrounds the main framework that is in between the outer frame surround and the main frame. Also sandwiched between the white plastic and the outermost frame surround is the tabs/boards that connect to the screen. Can I get some pointers or pictures on how to proceed and what to watchout for? I have to get it apart to get to the screws that hold the LED strips in Place.The Service Manual does not go into this much detail nor does it a part number for the led strips.
My plan is to carefully remove the strips then replace the bad ones and reassemble . I can take current readings on when done. I tried measuring the resistance on the plug but got OL on my Fluke 87 no matter what waythe leads were plaed. There was 4 wires a Black then Blue then another Black then Blue wire on a single plug. B side of power supply was cycleing on/off
never giving a 330 volts. A new P.S.did not help either. Last Resort Here.
Thanks Guys!

[mmartell]

Re: Dismantling Samsung 55 LCD LED Screens

The middle two wires (black and blue) are shorted on the power supply. The current runs through the left strip then back to the board then through the right strip then back to the board to complete the circuit.

Each strip is divided in half. The upper half and the lower half are run in series parallel. You have an open led in each of the top and bottom runs on one or both sides, that's the only thing that could make the string(s) go open circuit.

These strips generate quite a bit of heat though I'm not sure that's what's killing them. However it does seem prudent that jumpering open leds and not replacing shorted ones is a recipe for re-failure. When I reassemble my repaired strip I am going to put a bead of thermal paste down the mating side to help with heat transfer.

[Ltank]

Re: Dismantling Samsung 55 LCD LED Screens

OK Thanks, I will take pictures tomorrow.making notes from all the LCD LED listings to put to memory for future reference. the Pics will help others as you all have helped me.
thanks

[Ltank]

Re: Dismantling Samsung 55 LCD LED Screens

Well I took it apart. It was more of hassle than I thought it would be. Now I see why no one gets the Leds from bad screens for resale. There were two LED strips. One left and one Right. The Right side was on the left if veiwed from the rear of the set. It had 19 bad LEDs, 18 shorted LEDs and one was a Open. The other strip was fine,all its LEDs were good.
There were 100 Leds on each strip. 50 faced one way and 50 faced the other way. The connector from the PS had two sets of Blue and Black wires.
One set went to the Left and the other the Right. Then behind the screen
the Blue and Black wires were spliced to make two sets of Black and Blue wires to each LED strip. Now each LED strip had four wires to it two Blue and two Black wires,then on each connector at each strip had two sets of jumper wires that went to each LED strip. Now each LED strip were labeled as four channels. I had one that every LED lighted up and had good resistance on the diode scale. But the wiring matrix resistance was high and showed OL.
The LEDs are on a very thin layer of substate glued to the aluminum strip.
I can see it would be very easy for the 330 volts to short through, if that were the case. Tomorrow I will try to unsolder all the bad ones and maybe a good one so I can make and educated guess on a replacement LED.
The one is eating my Lunch but I am learning too. Cant charge alot of time on it but sometimes its the principal of it and you want to figure it out.
The screen had more layers than I thought it would. There was the Main frame that the LED strips mounted to it. Then there was a white plastic sheet with a smooth and a rough side. The rough side faced toward the screeen. Then there was a clear plastic over that then three different layers if diffusers then the LCD pannel. If there were more on the outside of the screen I dont know. I did not want to distub it too much. Now that i think on this it really bugs me. The screen was facing down when dissaaembled then we raised the backbone with the white and a few of the diffusers but we were careful to keep it in order. Just wish now I checked on layers in front of the screen. Now I am confused. If anyone knows the Layout order let me know.
This set was worked on before I got it.