Panasonic TX-50A400B No picture Backlights on

[london-freddie]

Hi got another one for you guys that has me stumped now
Not my tv looking at it for a mate from work
TV powers on backlights come on but no picture, he tells me it has sound but I have not heard any sound
My first thought was a mainboard problem, replaced the mainboard with a used board but still no picture
Moved on to Tcon board and replaced that, still no picture,
I do have 12v at the white tcon board fuse
Now I am stumped any ideas out there please where to look next
Just before posting this I removed one ribbon at a time from the tcon to panel
first ribbon off right hand side as looking down on the board gave me Half a picture
second ribbon removed made no difference no picture on other half

[diif]

Re: Panasonic TX-50A400B No picture Backlights on

Only half a picture suggests either a COF has failed or if you are lucky a capacitor is short. You should be able to get to it by removing the metal guard that covers it if the design is like the 50" Panasonic I did last night.

[london-freddie]

Re: Panasonic TX-50A400B No picture Backlights on

just refitted original mainboard so now has replacement tcon and same backights on no picture, removing ribbons gives same results one ribbon removed {right} gives half picture, left ribbon removed no change no picture at all but backlights still on
maybe a faulty panel
He tells me this tv is just out of warranty ?

[london-freddie]

Re: Panasonic TX-50A400B No picture Backlights on

will try and check the panel boards later, being honest, with it not being my tv I maybe do not want to put the same effort into it that I would if it were my tv

[diif]

Re: Panasonic TX-50A400B No picture Backlights on

Shouldn't need the panel stripping down, just 5 or 6 screws hold each cover on.

[london-freddie]

Re: Panasonic TX-50A400B No picture Backlights on

just got the covers off these panel driver boards, can not see anything obvious wrong

[diif]

Re: Panasonic TX-50A400B No picture Backlights on

What about testing the caps for shorts. It's rare to see caps that small burnt. It's the side that has no picture you need to test.

[london-freddie]

Re: Panasonic TX-50A400B No picture Backlights on

thanks for that diif do you know easy way of testing the caps on the board for short without removing them

[diif]

Re: Panasonic TX-50A400B No picture Backlights on

The way I test for shorts is put my multimeter into diode mode. Then the red lead on ground then probe with the black. A short is about 0v non short .5v

[london-freddie]

Re: Panasonic TX-50A400B No picture Backlights on

ok just spent some time checking caps on the driver board everything seems ok

[diif]

Re: Panasonic TX-50A400B No picture Backlights on

That suggests a faulty COF then, unless there's anything else on that board that could be faulty.

[london-freddie]

Re: Panasonic TX-50A400B No picture Backlights on

faulty board maybe ??

[comptek]

Re: Panasonic TX-50A400B No picture Backlights on

Check flex cables tcon- screen had 2 shorting tracks out before it was on a Samsung but still worth a try looked at it with an eye loop and I could see one track was out of line straightened it up and all was fine