Re: 50PB560B -LG common problems?
Is there any known way to test the logic board? It looks like I could buy one for around $50 with shipping but it would be kind of nice to confirm that it was the problem before spending this.
jp_fizzer
Member
Last Activity: 05-30-2020, 01:27 PM
Joined: 05-12-2020
Location: Dhahran
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Re: 50PB560B -LG common problems?
Here is where I am measuring Vsc on the Y buffer board. You can see from the picture that I get -23VDC when the TV is powered up but not working and I get 113VAC when the TV is working. Now the 113VAC does not seem to be related to the line voltage because I have tried it plugged into both 110V mains and 220V mains and this Vsc voltage reads the same.
Does this Vsc voltage provide any clues about what could be the problem?
Any suggestion what to test next? I have left the TV on in case there are any tests while it is on....Last edited by jp_fizzer; 05-16-2020, 06:24 AM.Leave a comment:
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Re: 50PB560B -LG common problems?
Here is the white label...Leave a comment:
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Re: 50PB560B -LG common problems?
Ok, I tried what the other poster did. I unplugged both the ribbon cable between control board and main board as well as the cable between power supply board and main board, inserted the jumper and plugged in TV. Nothing happened.
Then I connected everything back up again and the TV turned on. Since it was powered up I retested the voltages on the Y buffer board. The Vy is still 190V but the Vsc is very strange. When I put red probe on Vsc and black on chassis the meter just bounces on DC setting so I tried switching to...Last edited by jp_fizzer; 05-15-2020, 10:57 AM.Leave a comment:
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Re: 50PB560B -LG common problems?
Ah found it. Vsc to gnd is -23.5VLeave a comment:
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Re: 50PB560B -LG common problems?
I could not find the Vsc and Ve voltages. The Vy is 190V. Attached are pics of the Y buffer board....Leave a comment:
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Re: 50PB560B -LG common problems?
All of the voltages are the same when it does power up as when it does not power upLeave a comment:
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Re: 50PB560B -LG common problems?
After I plugged the ribbon cable in then I was able to get the TV to turn on. However, as soon as I cycle the power it no longer works.
It used to be that if I cycled the power several times eventually it would work. However that method stopped working a week ago so I decided to take the back off and see if I could figure out the problem. There was no obvious damage. I disconnected and reconnected all of the connectors from the power board and main board and then it worked again, once. As soon as I turned it off it would not turn...Leave a comment:
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Re: 50PB560B -LG common problems?
Yes, I just checked and I have VS on both pins 1 and 2 and I have VA on pin 6Leave a comment:
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Re: 50PB560B -LG common problems?
Now I have plugged the ribbon cable back in and turned on the TV and it worked fine. I turned it off and now it won't turn on again, although the standby light will switch.Leave a comment:
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Re: 50PB560B -LG common problems?
Ok, I unplugged TV, removed ribbon (you are correct, black tab lifts from left), inserted paperclip between two holes, plugged in TV.
The standby light came on but that was all. I tried turning the TV on and off several times but all that did was toggle the standby light, the screen never came on.Leave a comment:
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Re: 50PB560B -LG common problems?
Ok, so I am trying to connect the two holes, basically I want to connect the copper rings around the holes to each other?
For the black connector, am I slipping my fingernail under the ribbon edge (right side) and lifting, or the circuit board (left) side?Leave a comment:
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Re: 50PB560B -LG common problems?
Attached are photos of the back of the TV and a closeup of the Logic Board.
I really only see two small next to R451 and R452 and below it is a pad labelled Auto.
I am actually not really sure how to release that ribbon connector that goes to the main board. I assume I lift a clasp and then the ribbon cable will pull out but I cannot figure out what I am supposed to lift. I tried both the black plastic part and the silver metal part and neither want to lift easily. I figured I better ask before I break something. :...Leave a comment:
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Re: 50PB560B -LG common problems?
Oh wow, I am really glad I did not bake the boards.
So I see now why the 55V is correct on pin#6 of P811. That pin corresponds to VA which is supposed to be 55V.
Attached are photos of P811 and P813 (which is just the other end of P600 so they are exactly the same) and also a photo showing what the VS and VA voltages are supposed to be.
So the fact that when the TV is working properly pin#6 on P811 is the correct 55V but when the TV is not working properly it is 0V, does this tell me anything useful...Leave a comment:
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Re: 50PB560B -LG common problems?
Ok, so I did some more research on the subject and decided not to bother baking the boards yet. I put everything back together and the TV turned on. I cycled the power and it would not come back. So I unplugged all the boards again and plugged them back in. There was a huge spark when I plugged in the P811 connector but when I turned the TV back on this time it came back on. I have checked all the voltages with the TV on and they are all the same except that pin#6 on P811 is now at 55V where as it was 0V when the TV was plugged in but not working....Leave a comment:
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Re: 50PB560B -LG common problems?
So I have tried disconnecting all of the various boards one at a time and powering it up but never any difference so I have no idea which board might be the problem. I have read about some people having success reflowing the boards in their oven. As a last ditch attempt to revive the TV is there any point in putting the power board and main board in the oven?Leave a comment:
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Re: 50PB560B -LG common problems?
Hello, I have a 50PB560B and I started having an issue where I would have to try turning the TV on and off several times before it would finally turn on. The standby light would always go on and off, but the screen would just stay black. Now, I cannot get the screen to ever come on, although the standby light still switches when I turn the power on and off. I have thoroughly checked all the boards and cannot find any suspect looking components, no bulging, no leaking, no charring.
I have checked the voltages on the P600 connector...Leave a comment:
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