Samsung LN32R71BAX shuts down after 3 seconds

[Biruslapio]

Hi,i picked this tv up for repair,the initial fault was the side buttons board,it was malfunctioning(ch+ was increasing the volume etc),the owner smartly decided to aim a hairdrier at the board,which melted the plug connector,so he cut it,and thats how i got the TV,though it was going to be simple.

The tv powered by pressing the power button,which is toghether with the remote board.

First thing i did was solder the 3 wires back looking at how it was before
first wire=GND
second=KEY_INPUT1=100mV
third=KEY_INPUT2=3.3V
it did not work,i checked with an oscilloscope,INPUT1 is getting no voltage almost.

Got a samsung remote and it worked fine,the tv was fully operable with it,then all of a sudden it got stuck in store mode.

I entered the service menu and did a reset,it got out of store mode but nothing else changed.

I gave up on it for a few days and now,just plugging it into AC powers on after 3 seconds,the standby led is bliking once per sec,works fine only for 3 seconds,then shuts down,but the standby doens't stop blinking!
The power button now does nothing also with any button,but i can still shut it down via remote,then the SDTBY led stops bliking and is always on,try to power it up,same thing happens,can't mess with the service menu because there's no time for it to reset,maybe it'll only brick the tv even more.

I checked if it was only the backlight shutting down,aimed a flashlight,but no,the image really disappears,seems more like a main board problem.
24V that powers the inverter is fine,all the lamps are lighting up,12V,3.3V,5V,i checked them all with oscilloscope,nothing like bad ripple.

I already cleaned all the grounding points for every board,screws are tight,haven't found cracked solder joint or swollen caps.

Here are the pictures,the wires for the side panel board were soldered in correct order,i tore them apart just now for testing.

[dskall]

Re: Samsung LN32R71BAX shuts down after 3 seconds

Have you tried it with key pad disconnected?

[Biruslapio]

Re: Samsung LN32R71BAX shuts down after 3 seconds

Have you tried it with key pad disconnected?

Yes,it does the same thing,i can only think it's a mainboard problem,but i don't know how to solve it.

[Biruslapio]

Re: Samsung LN32R71BAX shuts down after 3 seconds

Update:managed to make the tv stay on by spamming on/off on the remote,but it only worked once,then the problem came back,i entered service menu(mute + 1 + 8 + 2) and quickly selected reset,that fixed the auto shut down problem,but now i'm back to square one,or zero,the TV doesn't respond to any button,just by plugging AC it turns on in 2 seconds.
KEY_INPUT1=100mV controls MENU,SOURCE,ON/OFF.
KEY_INPUT2=3.3V controls CH+ CH- VOL+ VOL-.
I monitored via oscilloscope when i press VOL+ for example the KEY_2 voltage drops from 3.3V to 2V,VOL- goes to 1.5V etc,so they are working correctly.pressing on/off drops KEY_1 100mV to 0mV,but the waveform is all noisy.
The only option for panel lock in the service menu is for when the TV is in hotel mode,and it's disabled,so no panel lock never,TV is on home mode right now.