Panasonic TX-40CX400B backlight problem

[Chrissygizmo]

Hi everyone, I'm new to this technology stuff apart from my school information technology lessons.

I can use a multimeter (only just) and a soldering iron.

Anyway my problem is on the above TV. Power Board model number 17IPS20. When turning it on the screen goes white, no picture or sound, then the white screen goes off. I've checked the led voltages and they are as follows

When white screen is on
White wire - 162.6v DC
Black wire - 0.0v DC

Then when white screen clicks off
White wire- 79.9v DC
Black wire- jumps to 40v & reduces to 10v DC

Any help would be really appreciated

I can post photos if required

Thank you for your time

Chrissygizmo

[dick_barton]

Re: Panasonic TX-40CX400B backlight problem

Any photo's of your boards. The power supply is 17IPS20-R?

[Chrissygizmo]

Re: Panasonic TX-40CX400B backlight problem

I have got these ones on my phone , if you need better ones let me know . Thank you

[Chrissygizmo]

Re: Panasonic TX-40CX400B backlight problem

I don't know if these photos are good enough, I will get better ones if your needing close ups etc . Thank

[dick_barton]

Re: Panasonic TX-40CX400B backlight problem

Whats the number in the red box? It looks like ending R9?
Can you give the voltages on the black connector that takes the power drom the power supply to the mainboard

[dick_barton]

Re: Panasonic TX-40CX400B backlight problem

With the set powered off remove the mainbpard from the power supply and connect +5V_STBY to ST_BY using a 1K resistor and also +5V_STBY to BL_ON-OFF using a second 1K resistor then switch on.

If the backlights remain on then it would appear to be a mainboard fault. If they fail then you most probably have a led(s) or led connection problem.

[Chrissygizmo]

Re: Panasonic TX-40CX400B backlight problem

Hi , sorry about the delay in replying, i really appreciate your help, I've looked at the photos I've uploaded and I can't see the red box you mean? I'm going to have another look at this tv soon so I will post clearer close ups later on tonight. I will also give what you mentioned a try and let you know the outcome.

[Chrissygizmo]

Re: Panasonic TX-40CX400B backlight problem

Just realised your picture with the red box DUH ! I will get back to you

[comptek]

Re: Panasonic TX-40CX400B backlight problem

Whats the number in the red box? It looks like ending R9?
Can you give the voltages on the black connector that takes the power drom the power supply to the mainboard

Looks like R9 to me

[Chrissygizmo]

Re: Panasonic TX-40CX400B backlight problem

Hi Thank you to all who commented on my thread, I have passed this tv on to someone else as I blew a few components on the power board while trying to repair it, it's a headache for the next person.