820-00821 fan spins but does not boot

[donnos]

Unit is very clean.. no water damage anywhere but does this funny boot sequence.

first cycle - fan immediately spins for 5 seconds and power cut off. during this, cpucore is 1.05v
2nd cycle - without unplugging charger, i get cpucore 1.05v for 5 seconds, but no fan spin. fan start spinning after that but vcore droppes to 0.55v

cpu vcore is 2ohms.. not sure where to go on now.

 

[2informaticos]

VCORE drops like in normal booting sequence.
Did you check for USB activity and external video?

 

[donnos]

No usb activity or external video as well.. Forget to mention on the second boot cycle lasted for 30 Seconds and it just shutdown itself

 

[2informaticos]

Try the board alone on the desk, nothing connected.
Then check for USB activity.
Also try turning on in SMC byapass and safe mode.

 

[donnos]

my bad here..i think this board won't boot without battery, so it was displaying the low battery icon but issue was no backlight so i was not able to see it. even under light it is hard but i caught it.

 

[2informaticos]

Usually new boards still boot without battery, but not all of them.
I don't know if is the case here; just test with known good battery.