Xbox 360 Slim - Without Video.

Hello, im pretty new here, so i apologize for any poblems.
Basically, i got a "new" X360 Slim. (Not the super slim).

i turn it on, and, well, no video.
Symptoms:
-No Video at all, i've tested both AV and HDMI.

-Powers on (Via Eject, Power button, can be powered by controller), and no RROD. Just the green led on.) It also does not make the boot up led animation.

-it reacts to eject, and the sync animation is somewhat bugged. controllers cant connect.

The PSU seems to be working fine. Orange on idle, green on powered on.

it is heating a little. so definitely the APU seems to be executing some code. (at least in theory).

The fan is correctly respoding to the fan curve set by the xbox.

i've confirmed it wont boot after some wait.

this is all that i have of info for now.

i've checked him on the sides to see if there is any RGH led on. i've seen nothing. im planning to crack it open (carefully) and give it a look.

My plans of fixing:
If it is RGH, i will give re-solder any cracked joints.

if is not RGH, i will need to diagnose what could be. i have no idea of how im doing that..

i will also put a little chispet heatsink on one of the components that seems to be responsible for this poblem. im not sure if it will help. but well, in stone age terms:
HEATSINK KEEP THINGS COOL, THINGS COOL NO POBLEM. roughly.

i want some help on diagnosing this poblem.

if its a issue that needs re-solding a chip, we will take to a technician to fix it. as we dont have the proper equipment. but i will happy to have some info on that. and if all is caused of those dirty temperature changes.