Plasma sony ke-p42m1 does not display nothing

[conan981]

Hi, i hope someone wants to help me in repairing this elephant i had for several months in garage.
Main fault is that TV does not display nothing (not even backlights are ON)
BUT led that is indicating that TV is on is GREEN.
(when you connect the 220v AC to TV led is RED, when you push power button led goes green)
Sometimes after 20 or 30 PUSH UP/DOWN of power button the tv GOES ON and is working OK..
Now, i found also SERVICE MANUAL of this TV that is downloadable HERE
https://cdn.badcaps-static.com/pdfs/...6e1dd1037b.pdf
with all the schematics and all the needed for repairing this, but i have only a little knowledge so i hope someone wants to guide me in repair.
I found that G1 board (this tv has 2 POWER SUPPLY BOARD) is working OK testing the voltage for the IN- connectors and the OUT connectors.
Found also that the backlights doesn't go on because there is no 170V (DC)
in CN6111 and CN6112 connectors.
Now, why there is no 170v?
I think that at page 33 of service manual there is the answer but i am not capable to understand what to test..
thanks for all the help you can provide me
Conan
ps. i don't know if are needed the same (having schematics) but here are some pictures of G2 board.
if needed i can make photos of the rest.

[drpj23]

Re: Plasma sony ke-p42m1 does not display nothing

Which 170v: Vs, Ve, Vset?

And yes, could you please take an overview shot of the whole back.
And then a more direct overview of the power supply.
All with no flash but ample lighting.

[conan981]

Re: Plasma sony ke-p42m1 does not display nothing

Here are the photos of the whole back of tv.i hope they are fine otherwise let me know.

Which 170v: Vs, Ve, Vset?

All the three.. i can measure VS = 6V , VE = 6V AND VSET = 5V

But i checked and 370V enter the g2 board. Maybe there is something like a stdby relay or similar that make the tv not switch to full on?

[gilly1984]

Re: Plasma sony ke-p42m1 does not display nothing

Blast a hairdryer on the power supplies before turning it on.

Does it switch on?

[conan981]

Re: Plasma sony ke-p42m1 does not display nothing

@gilly1984

heating G2 power supply board the LCD PANEL goes ON!!
what should i check?
thank you

[tom66]

Re: Plasma sony ke-p42m1 does not display nothing

Cold joints! Older Sonys were well known for it. Re-touch any suspect solder joints. Try narrowing down heat location.

Oh, and minor nitpick: there's no LCD panel in a plasma TV .

[conan981]

Re: Plasma sony ke-p42m1 does not display nothing

@tom66
ehehhe sorry mate

btw, after resoldering G1 power supply area near 370V now the TV goes on all the times!
BUT... there is a BLACK STRIPE on the left that was not there before...
and a nasty noise that is coming from the part i attached in photo 2 in this post. like a BZZZZ
seems to be an endless story
what should i check now?
thanks to all

[tom66]

Re: Plasma sony ke-p42m1 does not display nothing

Older plasmas buzz a lot, put the case on, won't be audible from 10 ft viewing distance.

As for black strip, you need to take the bottom buffers off and inspect the flat flex drivers, may be a bad driver (=bad plasma panel) but I am aware the older ones commonly had cold joints, especially if it is intermittent, it is likely another cold solder joint

[conan981]

Re: Plasma sony ke-p42m1 does not display nothing

@tom66
thank you for your suggestion tom, but i don't understand very well what to do.
in attachment there are the only flat cables i found, are these that i should check or there are other ones? what should i do to check them?
thanks again

[tom66]

Re: Plasma sony ke-p42m1 does not display nothing

No sorry, from the bottom of the panel... you may have to take off the main board.

[conan981]

Re: Plasma sony ke-p42m1 does not display nothing

just to close this adventure, i found the flat cables tom66 told me on the bottom on the tv.
the first one on the right (staying behind the tv) was the bad_guy.
i had to remove all the panels to reach the flat cable, btw i had to resolder 2 resistors on the flat cable and all went to the life again. Now tv is working perfectly
Really thanks to everyone here!

[tom66]

Re: Plasma sony ke-p42m1 does not display nothing

Enjoy your TV!

[Macedopt]

Re: Plasma sony ke-p42m1 does not display nothing

Hi,

Sorry to bring back the post, but im in serious need of help, hope i can count on you guys XD.

So i have the same tv thats here, but cant manage to put it working, the failure is basically the same, i can put it to work only with a mere 10 secs of blasting hot air gun (about 350 c) in the top corner of the g2 power supply, so i resoldered most of the b side of the board execpt the smd components, and cant manage to put it working, but evrytime i use the air gun it works failing if i let it complety powerd off for about 15 min.

Dont know what to do here do you gys can give some advice

thank you very much

[tom66]

Re: Plasma sony ke-p42m1 does not display nothing

Perhaps try concentrating your heat in certain areas such as electrolytic and ceramic capacitors, both of which can become temperature sensitive over time.

[Macedopt]

Re: Plasma sony ke-p42m1 does not display nothing

Thanks tom66

So youre saing that the caps might be ruined?

[tom66]

Re: Plasma sony ke-p42m1 does not display nothing

Possibly, though ruined may be too far -- they are replaceable.

[Macedopt]

Re: Plasma sony ke-p42m1 does not display nothing

Ok,

just tried to heat difrent zones on the g2 board, 10 sec of air each, and no matter where i place the air it turns on, it cant be could joints because i dont stay long enough for it to melt.

dont know what the hell is happening to it.

any toughts guys

thks

[Macedopt]

Re: Plasma sony ke-p42m1 does not display nothing

Hi,

So i run another tests and it seems theyre 2 places where i can heat and tv will go on, as shown in the picture, i have resoldered pretty much evrything on those areas, and still nothing, when the hardware gets cold i cant get no image.

Notice that i only heat for about 5 sec, about 350 degrees, wich i believe is not enough to melt the solder.

As tom66 said it might be bad caps, but i wanna be sure, cant the transistrs or maybe thos chips be heat sensitive, in my area caps are expensive and hard to get, i know i must try because theres no guarantee in this kind of things, although just want to have more certanties.

sry for my very bad english

and thank yu very much for the help.

[tom66]

Re: Plasma sony ke-p42m1 does not display nothing

It's not melting solder that you're trying to do; you're trying to make a cracked solder joint expand, which even low temperatures will do.

[Macedopt]

Re: Plasma sony ke-p42m1 does not display nothing

so you believe its cold joints il try look closer, the only thing is that no matter where i heat, on those places, it will get on.

thank you