VPC-Z1 No Power Suddenly, Charge Light blinks

Hello,

My VPC-Z1290S suddenly shut down the other day, running on battery while browsing the internet (nothing processor intensive), on battery power (plenty of juice).

I plugged it in, powered on, it got to the Windows logo, and suddenly shutdown again. I unplugged, let it rest for a bit, then plugged it back in, booted, got to the BIOS screen, then it shutdown again. Now, it will not power on at all, sometimes the green power light goes on for ~1 second, then fades off. Usually nothing happens.

If I plug it in with the battery, the charge light comes on for 1 second, then turns off [Correction, the battery will charge continuously until full, so charging circuit works].

Any idea what this could be? Troubleshooting tips?

Theoretically, if the CPU is fried, would the above happen? I'm trying to see if it's a CPU issue or maybe a short on the MB that's causing this.

What I tried:
- Verified DC power with VM (19.5V).
- Disassembled everything and put it back together.
- Removed from power overnight and attempted restart.
- Tested CMOS battery (~3V)
- All these scenarios tried powering on with battery only, plugged in only, or both.

Any help would be much appreciated.

EDIT:
Also tried:
- Booting with 1 RAM stick, or no RAM sticks. Same result
- Booting with every ribbon cable detached, same result.

 

You could try a "reset":

unplug AC adapter
remove battery
press and hold power button for 30 seconds, then release
install battery
plug AC back in and turn on.

this worked for my SR when it would not turn on.

 

I tried this "reset" before all the scenarios above. I believe it's a mainboard issue, which is probably not worth replacing anymore; I was hoping that I can somehow localize the problem and fix it.