ok! so today i decided to pick this thing up again for more testing, and i had given up on this laptop so i just turned the current to the max, at 3v and that surprisingly was using 10w, so i start poking around with my finger and found a seemingly empty spot on the board getting uncomfortably hot after a few seconds. i turned the board around, and i don't see anything, just some tape+shielding material that i had completely ignored last time, so this time i just peeled it off a little bit not expecting to see anything there, but this is what i found. this IC by the USB ports(in the attached image (it looked physically ok)). i removed it, tested again, this time the draw was about 3w, but it was getting hot in the same area, so i completely removed the tape and found another identical IC also getting very hot. I removed that one, and the short on the 3v rail was gone.
while removing the originally exploded IC, i accidentally removed some passives around it, easy enough to repopulate. But! now that i found the short on the 3v rail, i wanted to try powering up the laptop using the soldered wires that i used to find the short to get 3v up.
I tried this, and nothing at all happened. no charging lights, no signs of life at all. i only supplied +3VALWP, but the exploded IC also seemed to supply +3VLP. Looking at the power sequence, +3VLP comes on when the power button is pressed, or 2.23ms after AC_IN, not clear if it's the delay that brings it on, or if it's the power button press.
What would you recommend? should i also supply +3VLP with another psu?
as i'm still broke, i think i would only buy the exploded IC if it was confirmed that the problem is gone, but maybe that IC itself is necessary to dtermine if the problem is gone.
It's been about a year now since this died, and i've been taking a look at it every now and then, to see if i come up with something, and today has been the most productive day in finding the problem with this laptop!