LED TV Driver circuit

[tech2014]

Can someone tell me what the normal voltage would be in an LED driver circuit, for a 60" Panasonic LED TV model TC-60AS630U. I am looking at schematic in the service manual, but it doesnt show a voltage. Would around 100v be a proper voltage. I only get 25V in standby and full power mode, but get no screen. The backlight never comes on,not even for a second.

[cliff_hootarski]

Re: LED TV Driver circuit

Look at the voltage rating of the electrolytic caps on that supply. For example a 200v rating, the output of the circuit will be less than that for a comfortable safety margin.

[budm]

Re: LED TV Driver circuit

Can someone tell me what the normal voltage would be in an LED driver circuit, for a 60" Panasonic LED TV model TC-60AS630U. I am looking at schematic in the service manual, but it doesnt show a voltage. Would around 100v be a proper voltage. I only get 25V in standby and full power mode, but get no screen. The backlight never comes on,not even for a second.

Can you upload the circuit/service manual?
Sounds like the boost converter is not working or the LED driver is not getting the bl-on.

[tech2014]

Re: LED TV Driver circuit

Can you upload the circuit/service manual?
Sounds like the boost converter is not working or the LED driver is not getting the bl-on.

Here is the service manual. Had to pay $20 for it so please pay it forward and post in on toms and/or any other site.

[budm]

Re: LED TV Driver circuit

PDF page 24 shows the BL-ON command pin.
Not much of the service manual at all.

[budm]

Re: LED TV Driver circuit

BTW, we will need good clear pictures of the whole backside of the TV showing all the boards, and good clear pictures of the LED driver board.

[tech2014]

Re: LED TV Driver circuit

BTW, we will need good clear pictures of the whole backside of the TV showing all the boards, and good clear pictures of the LED driver board.

I get 0.007V on the BL_ON pin 13 of power connector P2. I get my standby, 16v and 24V. Is it possible to jumper 5v standby to BL_ON to force on the BL.

[budm]

Re: LED TV Driver circuit

So you have 24VDC on connector P4 Pin 6.8, 9 to power the LED driver board which I do not see it in your pictures, you also have BL-ON. So now you need to get to the LED driver board to see what it has on the that board, may be fuse or what ever.
Also check the error signal pin 4 (BL-SOS) which I am not sure if NORMAL = HIGH or Normal = LOW.

[budm]

Re: LED TV Driver circuit

BTW, PDF page 16 shows the lLED blinking codes, what do you see on your TV?

[tech2014]

Re: LED TV Driver circuit

So you have 24VDC on connector P4 Pin 6.8, 9 to power the LED driver board which I do not see it in your pictures, you also have BL-ON. So now you need to get to the LED driver board to see what it has on the that board, may be fuse or what ever.
Also check the error signal pin 4 (BL-SOS) which I am not sure if NORMAL = HIGH or Normal = LOW.

Isn't BL_ON supposed to be 3-5 volts,I get 0V.

[budm]

Re: LED TV Driver circuit

Isn't BL_ON supposed to be 3-5 volts,I get 0V.

OK, I got you mix up with other thread, you DO NOT have BL-ON signal.
But what LED blinking code are you getting?

[tech2014]

Re: LED TV Driver circuit

I don't see any flashing from the power LED. It either stays Red or no led at all. I do not have BL_ON

[budm]

Re: LED TV Driver circuit

At this point it points to the main board problem, if the main board is OK then it should show error codes.
Look real close at the main board top and bottom side for any damages, fuses, etc.
What is the history of the TV?

[tech2014]

Re: LED TV Driver circuit

So the BL_ON command does comes from the main board?

[tech2014]

Re: LED TV Driver circuit

I tested the voltages on the main board and I am missing the PNL12V TP4000/TP4001 12V. I get 0.017V at SRV-12V on the main board. I did the flashlight test and saw no video.

[budm]

Re: LED TV Driver circuit

No PNL12V then there will be no DCV to run the T-CON either.
BL-ON, DIM, PS-ON, DIM: these signals are generated by the main board, just like other LCD TVs, same principle, you should know that by now.

[tech2014]

Re: LED TV Driver circuit

No PNL12V then there will be no DCV to run the T-CON either.
BL-ON, DIM, PS-ON, DIM: these signals are generated by the main board, just like other LCD TVs, same principle, you should know that by now.

umm, yeah I do know. Found missing voltage on the main board. Found a buck converter IC with no output voltage. I replaced it and no joy.

[tech2014]

Re: LED TV Driver circuit

So your sure the panel12V comes from the main board. I did continuity checks on main board and only found the 12v at the one pin of the buck converter. The 12V goes to the T-Con, could a TCON problem on the 12V line kill the 12V.

[budm]

Re: LED TV Driver circuit

Some TV will have separate connector on the T-CON so it will get the switched PNL-12V from the POWER SUPPLY board, the power supply will have to receive PNL-12V ON signal from the main board for the power supply to send out the PNL-12V.
As you can see, your T-CON board does not have separat connecortor for the PNL12V, so that means the 12V run the T-CON is fed through the LVDS cables which are connected to the main board, so if you think about it, where would the SWITCHED PNL12V will come from. The main board receives the 16V from the power supply board, then that 16V gets distributed.

"So your sure the panel12V comes from the main board."

Look at the PDF page 23, 24 on how the PNL12V is generated from the incoming 16V (its name is changed into F15V).
That 'DCDC PANEL12V' has to be working first, that is what you need to do, as you can see that IC5300 is a buck converter that can be switched ON and OFF by the command signal 'PANEL_VCC_ON2'