Random shutdown & 7805u refuses to boot up again (sometimes)

Had my 7805u for about a year and a half now. I have tinkered with it previously to upgrade parts but this particular problem has never occurred before so i highly doubt it is related to the CPU/SSD/BR drive/Heatsink mod upgrades that i have carried out.

Basically, my 7805u spontaneously shut itself down (idle temps on my X9100 were at 39C at the time) and then refused to start up again - pressing the power button (repeatedly) did nothing at all. It only managed to briefly light up the HDD status indicator for one second per power button press.

At first, i thought it might be my power brick so i unplugged the power cord and tried running the notebook off the battery. I managed to get into windows but the 7805u decided to switch off again. Same symptoms displayed as previously described in 2nd paragraph.

I then tried removing the battery and running off the power brick again. My 7805u again managed to get into windows but turned itself off halfway through chkdsk diagnostics. No success with pressing the power button to turn it back on; only managed to light up the HDD indicator light for 1 second.

Then tried running on both power brick + battery (7805u detects battery plugged in by "battery charging" blue status light). Had some trouble starting the 7805u but it did manage to get into windows before a random shutdown occurred again.

Currently testing out my 2x 2GB RAM sticks as i am suspicious that this might be the source of the problem. I'm assuming faulty RAM would prevent bootup or cause random shutdowns. Then again, if only 1 stick is bad, can the 7805u still boot up via the other good stick even though both are plugged in?

I dont think it's the battery/power brick and/or mobo issue.

Any further insight or advice would be highly appreciated. I use my 7805u on a daily basis for PhD research needs + home entertainment so i would like to diagnose and fix this issue ASAP.

cheers

 

If you can plug it in powered off see if the brick shows its led on. if so then the battery may be getting a charge. Let it cherge a bit and see if you can power up. My first brick I had would work under low load but if you tried to power up it folded and you would see the light on the brick die out.

 

LED on brick always shines green - guess that's indicative of its "ON" status.

both RAM sticks tested ok. Problem seems to have gone away now. Only time will tell.