820-2915 sometimes boot sometimes no

[donnos]

820-2915 came in for GPU Bypass as screen was showing artifact. Successfully Flash Gmux, boot up fine and returned to customer.
next day customer says laptop does not start, brought back and checked

Fan spins but does not post.

cpuvcore start with 1.15v and goes to 0.75V and jumps between 1.15 and 0.75v

load from PSU also jumps around from 700ma to 1.1A like there is activity.
Board will boot when seated awhile and becomes warm from here on no issues. but shows symptom again when board cools down.
already tried flashing bios and clearing ME
i know that tantalum cap has this effect on other models, any common caps for this model? or totally different issue here

 

[2informaticos]

Did you remove R8904/11?
Tried different RAM modules, one at time?

 

[donnos]

Yes R8904 is removed,

Tried the Ram, with new one as well. Thing is that it didn't beep like regular when no RAM was connected.
And actually i just realise that the front white status light will blink 5 times and stays dead. what does 5 blinks mean?

 

[2informaticos]

Did you test the board alone on the desk?
You must get steady 0.75V at VCORE.

 

[donnos]

reading was done with only board + RAM, nothing else installed

 

[2informaticos]

Check if boot in SMC bypass mode.

 

[donnos]

i tried PRAM Reset, at least now i hear the chime, so its in fact boot looping with hdd plugged in. without hdd it chime once and nothing running after that.

in SMC Bypass mode its also boot looping with max fan spin.

 

[2informaticos]

I suppose GPU issue...

 

[donnos]

But GPU is already by-passed? should i just remove it?

 

[2informaticos]

Do GPU disable again, just in case.
If still the same, then try removing GPU chip.
Let R8904/11 out from start.

 

[donnos]

Reflash Gmux again, same
remove GPU , same.
notice cpu and gpu both have been messed with previously.
no display on external as well
anymore ideas?

update*** i see display once!! loading bar went up to about 70% and went dead again. i guess its cpu