50PB560B -LG common problems?

[dick_barton]

Re: 50PB560B -LG common problems?

That seems awful low but I'm unfamiliar with the layout of this buffer. Normally it is measured across a resistor.
Perhaps someone else could offer advice here.

The only other thing is to try and get the set two switch on again and then measure +Vsc once again.

The white label on the back of the panel can you post a picture of it because it does give information.

[dick_barton]

Re: 50PB560B -LG common problems?

Just seen this in another post relating to this model. To run the self test successfully

Originally Posted by tvtimmy View Post
Unplug the ldvs cable(flat one) that runs from the Main board to the control board and put a piece of wire in the holes on control board marked r451 and r452. If you have test patterns and colored screens your main board is bad.

Hi, did what you suggested, and still wouldnt turn on, so unplugged the cable from PSU to main board, and it turned on, then did what you said and got test patterns

[jp_fizzer]

Re: 50PB560B -LG common problems?

Just seen this in another post relating to this model. To run the self test successfully

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 AC and it is pretty steady around 120VAC, which is the line voltage I am plugged into. I switched back to DC and reversed the probes so black on Vsc and red on chassis, it is bouncing around 6-8 VDC.

Edit: I re-tested Vsc, this time using my Fluke T5 which has voltage autoselection and it is giving me 113VAC, so definitely it is thinking it is AC basically line voltage. This is while the TV is working.

[jp_fizzer]

Re: 50PB560B -LG common problems?

Here is the white label

[dick_barton]

Re: 50PB560B -LG common problems?

All your voltages appear to be good other than Vsc whcih I'm unsure how or where you measure it. Hopefully someone else can provide an answer.
The other person did get the test pattern to run so I'm suspicious of your logic board.
At this point I am out of any further ideas but hope you get some more help from other forum users.

[jp_fizzer]

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. As soon as I turn it off it will take many tries to get it to come back on again.

[dick_barton]

Re: 50PB560B -LG common problems?

If the set powers up and all the voltages appear to be correct and if we ignore Vsc for a moment, what you do know is that the set will not go into self-test mode, then perhaps there's a problem with the Logic board.

[jp_fizzer]

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.