Panasonic TC-L32C22 Backlight issue.

[martino]

Gentleman:Got a fun one here....
TV,when turned on will try for about 20 seconds to startup.
In that time you can see the backlight is flickering erratically as in trying to turn on.After about 20 sec it gives up and goes into SOS1=backlight failure.

Now,when I opened her up,I saw cap C7829 being bulged and being REVERSED polarity on the board!!! No sign of it ever being soldered.!
I replaced it,polarity correct this time,no change....

I did a lot of tracing the board and measuring and I'm getting some fluctuating voltages in the 12v line(11.9 v to 7.2 and back etc) Even with 7.2v it will still try to turn on backlight.

Voltage to inverter coils,according to schematic,should be 34v,I'm getting 2.4v max.

Anyways,before getting carried away into the power supply,I would like to ask the pro's here,how to force the power supply on(with inverter) to eliminate a mainboard problem.
Pic#3 shows the pin out for plug between PSU and main board.
Do I jumper between pin#1&pin#13 or #14 or both? Resistor needed?
Once I can force PSU on I can trouble shoot a little better(20sec time frame gets annoying after a while,lol)

Hope you can help

Tom's SM:
http://www.toms-service-manuals.com/...h=Submit+Query

PSU:TNPA5123
Main:TNPH0856

[martino]

Re: Panasonic TC-L32C22 Backlight issue.

Gentle bump

Anyone knows how to force on the psu without main board hooked up?
Pin out is in pic3 in first post.

[martino]

Re: Panasonic TC-L32C22 Backlight issue.

Fixed it

As mentioned in post#1,C7829 was reversed polarity right out of factory.
Looking deeper into the 12v feed,I found out that C7829 is some sort of filter cap for the 12v feed,it sits between 12v and ground.When tv was trying to turn on the backlights I could see that 12v dropping from 11.9v to 7.2 fluctuating.
Tracing the 12v back to source,I found a resistor in series,right after the 12v gets rectified,a 1ohm tiny resistor.Measured it and it was 387 ohm!!!
Replaced the resistor and TV came on beautifully and 12v feed stays perfectly at 12.1v now

So,I'm thinking that the reversed cap had put a strain on that resistor for as long as the TV lasted and finally failed enough to get inverter issues....

Anyways,it's a fix,I'm proud of myself,took a while for me to find it as that resistor was far away from the whole inverter circuit. Really starting to love this component level repair appose to simply buying replacement boards....
My wife watched me of and on while I was working on this PSU and thinks I'm totally Einstein now lol

On to the next one

[porrascarlos80]

Re: Panasonic TC-L32C22 Backlight issue.

hi, congratulations great finding!

I have a problem with my panasonic tv 32 lcd , same board. TV its dead no lights no signs all dead.

newbie here.

how can I test output voltages from this board? I read somewhere applying 5v dc to pin 10 will power it on, right?

do you remember which resistor failed how can I locate it on my board and test it before going elsewhere?

any advice, guidance its more than welcome, thank you!