Hello guys. I'm new here but I have done a fair amount of research on this TV. Long story short I picked this 70" TV as non working unit for $20 today. Yes I know they were recalled. However according to the serial number this one was not one of the affected units. Anyway this TV is 4 years old. The person I got it from told me he was watching the TV and it just went out and would not power on. I knew when I got it that they were recalled and known to have the infamous black screen of death and that the lcd panel itself goes bad. I figured for $20 its worth a shot in the dark. I'm a automotive technician by trade and have done my fair share of electrical nightmares on luxury cars. So nothing surprises me anymore. Also on that note yes I know there are numerous threads on this particular TV. I have been through most of them but couldn't find the answers I am looking for. So onto the details.
The previous owner stated tv just stopped working would not come back on. He wasn't able to tell me wether it still had sounds or not. He did say before it went out it made a very bight flash and went out.
So fast forward to me tear down and diagnosis. When I got it home I did a hard reset and discharged the capacitors as well. To no avail,when powered one the led would flash a few times and go back out. Then I could turn it on the whole screen would flicker and go out and make this static type noise like something was shorted. Also by screen I mean the back light would flicker once and go out. So I thought ok maybe just the back light circuit is the issue or the power supply board as the circuit is on that board.
So I took the back panel off removed the power supply board and inspected it closely at first I didn't see anything but after flexing the board here and there I found 2 cold solder joints on one of the yellow capacitors on the board. So I resoldered the 2 clearly cracked joints and viola the back light was fixed and now the TV stays one just no picture. So with the back light issue sorted I thought maybe I have a power supply issue or standby power issue from power supply board to the main board.
But I checked standby power and it shows 3.3volts so I know thats good. So I decided to check the remaining pins and it all looks good except for the main board. So I am getting 12v in pin 1 on one of the ribbon cables going to the TCON board but nothing on the second ribbon cable on pin 1. This panel is split into 2 halves. It looks like the main board isn't sending 12v out to one side of the panel. So when checking the TCON board and checking the contactor I get 15.5v on the drain,gate gets 0volts as does the source. I had luck disconnecting the one ribbon cable from TCON board and only half the screen was working but had some lines through it. Now I cant get it to do anything. My question is this, could my issue be the main board as its not sending out 12v for the second ribbon cable. I mean this makes sense. being that before I could disconnect one ribbon and have half the panel working but now I still only get 12v on the one ribbon cable but the panel is dead nothing works even when disconnecting the other ribbon to have half the panel work. I am open to suggestions. Wondering if theres any more diag that can be done on the main board before replacing it.
The previous owner stated tv just stopped working would not come back on. He wasn't able to tell me wether it still had sounds or not. He did say before it went out it made a very bight flash and went out.
So fast forward to me tear down and diagnosis. When I got it home I did a hard reset and discharged the capacitors as well. To no avail,when powered one the led would flash a few times and go back out. Then I could turn it on the whole screen would flicker and go out and make this static type noise like something was shorted. Also by screen I mean the back light would flicker once and go out. So I thought ok maybe just the back light circuit is the issue or the power supply board as the circuit is on that board.
So I took the back panel off removed the power supply board and inspected it closely at first I didn't see anything but after flexing the board here and there I found 2 cold solder joints on one of the yellow capacitors on the board. So I resoldered the 2 clearly cracked joints and viola the back light was fixed and now the TV stays one just no picture. So with the back light issue sorted I thought maybe I have a power supply issue or standby power issue from power supply board to the main board.
But I checked standby power and it shows 3.3volts so I know thats good. So I decided to check the remaining pins and it all looks good except for the main board. So I am getting 12v in pin 1 on one of the ribbon cables going to the TCON board but nothing on the second ribbon cable on pin 1. This panel is split into 2 halves. It looks like the main board isn't sending 12v out to one side of the panel. So when checking the TCON board and checking the contactor I get 15.5v on the drain,gate gets 0volts as does the source. I had luck disconnecting the one ribbon cable from TCON board and only half the screen was working but had some lines through it. Now I cant get it to do anything. My question is this, could my issue be the main board as its not sending out 12v for the second ribbon cable. I mean this makes sense. being that before I could disconnect one ribbon and have half the panel working but now I still only get 12v on the one ribbon cable but the panel is dead nothing works even when disconnecting the other ribbon to have half the panel work. I am open to suggestions. Wondering if theres any more diag that can be done on the main board before replacing it.
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