Sharp Aquos LC-60LE635E three blinks

[klassic]

Hi community,

I will describe my problem with a TV in those short following terms to be the most precise :

What i have :
Sharp Aquos LC-60LE635E
power board DPS-162KP-1
main logic board QPWBXF733WJN2

symptoms :
white led light logo at startup,
after 2 minutes, blinking 3 times a row, repeating
no backlight (and apparently no picture, checked panel with flashlight)
no startup sound

powerboard investigations :

1-2 PNL : 0v
3-4 GND
5-6-7-8 UR : 13.15v
9-10-11-12 GND
13 AC_DET 3.29v
14 PS_ON 2.84v
15 BU5V : 5v
16 PNL_POW : 0v
17 PWM1
18 x
19 DIM
20 x
21 OFL : 0v
22 ERR : 0v
23 PWM2
24 STB :0v

i have 400v at the big caps
if i short BU5v and PNL_POW together, board alone and separated, i get 12v at 1-2pins PNL
i have nothing at the backlight connector

mainboard investigations :

13.12v is going into a bunch of step down regulators
i get several voltages from here, 3.3v , 5v, 1.74v and other voltages (if i measure them right, i'm not 100% sure)
there seem to be a smd led near cpu, no blinking

any ideas ? I've have my own, but i wouldn't like to influence you if i'm wrong

thanks for advices in advance, it's my first head scratching (no bad capacitor) repair and i've learned what to check here

[klassic]

from my investigations, i think, but not sure, that my main logic board is dead ?