Panasonic TX-L42WT50B half dead

[tmaster21]

Hello. yesterday i went to shopping and i found an panasonic 47" tv with very good looking at side of garbage bin... well was free.. i took it

like i explain on my presentation ,i work on computers daily but i never touched on one of this smart tvs, and i have been learning online how they work,what is an t-con and this kind of stuff that don't exist on computer or laptops.

the symptom is : if i press power ,it shows solid red light(on) but nothing else. No screen ,backlight, sound nothing. And after 5 to 10 minutes start blinking 13 times , second manual, means a-board Fail(mainboard)

I take a look on service manual: downloaded from here: (attachment)
and all voltages checked.All voltages are ok(15v,3.3,1.1) ,no shorts to ground, steady 15.28V on psu, except PNL12V to T-con unit that is off . Second manual its supplied by IC5300 regulator, that is not enabled(pin1) while power led it's on, like i think it should. The only chip that gets warm is the cpu (ic8000)and i notice that is an missing heat pad from one of the 4 hynix ram memories(missing from factory,what quality check!),but i don't think that is the problem because ram modules can work without heatsink.

for you guys, that are way more experienced on tvs than me,what is happening here?
broken solder on cpu?

There is any trick to test t-con and panel(leds and led controller board) without main board to check if they work? right now once t-con it's no powered i's all off.

fotos for reference:
original links:
https://ibb.co/bQv08sc
https://ibb.co/TPhGhJM

[dick_barton]

Re: Panasonic TX-L42WT50B half dead

You don't mention the 16V which is regulated down to provide by IC8101, IC8100 etc as shown on page 27 of the manual.
There's 15V shown at Pin 12 of connector A10 and 16V at connector A02 pins 1,3 & 5

[tmaster21]

Re: Panasonic TX-L42WT50B half dead

yes, it's there. I assume that was 15v because measured 15.60V that feeds that regulators.i measured again right now.

[tmaster21]

Re: Panasonic TX-L42WT50B half dead

update: today i try an jumper wire from 3.3v sorce direct to pin 1(enable) from driver(ic5300) and that enable the 2 high and low side mosfets and 12v reached the t-con. So PNL12v line its OK . its just the cpu that don't enable it on power on... it's comon cpus stop working on that tvs? On computers i can't remember the last cpu that i change...

[nomoresonys]

Re: Panasonic TX-L42WT50B half dead

Indeed tv mainboard bga chips go faulty, usually with bad solder connections, much more often than pc cpu's.

[tmaster21]

Re: Panasonic TX-L42WT50B half dead

Any one have experience on reflow this cpu chips on tvs? I see that the mainboard is very thin ,almost half of laptop board.
My idea is flux with liquid flux under the chip, and heat up a bit . i still have to see times and temperatures!? ,and i'm afraid that board bend with heat... any recommendations?

[nomoresonys]

Re: Panasonic TX-L42WT50B half dead

Check youtube, yep use liquid flux, try to get it under with good coverage, the general idea is to get it up to temp to melt the solder, so about 225-240 C about 450 F or so, try to bring the temp up very gradually once up to temp for about 30-60 seconds, then bring it back down gradually so as not to thermal shock anything, using tin foil or some such to try to protect the small surrounding components from falling off. Use caution too little heat won't hurt just won't help any but too much heat can kill the chip.