I'm not the original owner.
Initially the screen wouldn't turn on when powering on the laptop (and in some cases it wouldn't shut down when pressing the power button; had to remove battery and AC). Since I found out that it may be caused due to bad RAM, I opened it up and removed all RAM sticks (including the ones under the keyboard), added a single RAM module known to be working, did a hard reset (remove all power sources and press the power button for 1 minute) and the screen and keyboard light came on and eventually got the BIOS screen. Yay!
Now the issue is that it won't stay powered on for more than ~15 seconds. Also the power on behavior is a bit inconsistent. Boo!
After a hard reset, on the first power on (with me mashing the F2 key), it lights the indicator leds and after a 10-15 seconds the fans start up hard and it powers off.
On the second power on the keyboard and screen light up and the screen is black; after 10-15 seconds it turns off, no fans.
On third power on, it displays the BIOS screen (BIOS version 204) where I can see the CPU, RAM and HDD; after a few seconds the screen freezes (initially thought the keyboard was disabled however the seconds on the displayed clock don't change) and after another 2-3 seconds it powers off with the fans lightly running.
On further power on attempts it cycles through the previous scenarios, but I didn't document the order and the fans may or may not turn on. Never saw a POST screen and never heard any beeps.
Since the fans kicked in and I felt like the time between power on and power off was getting slightly smaller between consecutive attempts, I thought it might be a overheating issue. As a result, I dissembled it completely, cleaned the fans (they were NOT clogged), removed all non-essential components (blu-ray, wifi, usb hub) and even replaced all the thermal grease from the CPU and GPU. Same outcome and when scanning the motherboard and graphics card, after it powered off, with a laser thermometer I could not find a spot that was more than 38-40C.
Lastly, I tested the CMOS battery and it checked out fine.
I am willing replace a single component in a final attempt the fix it. What component could most likely be at fault? Motherboard, CPU, GPU?
Or is there another arcane technique I can try?
Thank you for going through the whole post.
Note: I doesn't seem to matter if I power it on with only the battery in, only AC or both.
Initially the screen wouldn't turn on when powering on the laptop (and in some cases it wouldn't shut down when pressing the power button; had to remove battery and AC). Since I found out that it may be caused due to bad RAM, I opened it up and removed all RAM sticks (including the ones under the keyboard), added a single RAM module known to be working, did a hard reset (remove all power sources and press the power button for 1 minute) and the screen and keyboard light came on and eventually got the BIOS screen. Yay!

Now the issue is that it won't stay powered on for more than ~15 seconds. Also the power on behavior is a bit inconsistent. Boo!

After a hard reset, on the first power on (with me mashing the F2 key), it lights the indicator leds and after a 10-15 seconds the fans start up hard and it powers off.
On the second power on the keyboard and screen light up and the screen is black; after 10-15 seconds it turns off, no fans.
On third power on, it displays the BIOS screen (BIOS version 204) where I can see the CPU, RAM and HDD; after a few seconds the screen freezes (initially thought the keyboard was disabled however the seconds on the displayed clock don't change) and after another 2-3 seconds it powers off with the fans lightly running.
On further power on attempts it cycles through the previous scenarios, but I didn't document the order and the fans may or may not turn on. Never saw a POST screen and never heard any beeps.
Since the fans kicked in and I felt like the time between power on and power off was getting slightly smaller between consecutive attempts, I thought it might be a overheating issue. As a result, I dissembled it completely, cleaned the fans (they were NOT clogged), removed all non-essential components (blu-ray, wifi, usb hub) and even replaced all the thermal grease from the CPU and GPU. Same outcome and when scanning the motherboard and graphics card, after it powered off, with a laser thermometer I could not find a spot that was more than 38-40C.
Lastly, I tested the CMOS battery and it checked out fine.
I am willing replace a single component in a final attempt the fix it. What component could most likely be at fault? Motherboard, CPU, GPU?
Or is there another arcane technique I can try?
Thank you for going through the whole post.

Note: I doesn't seem to matter if I power it on with only the battery in, only AC or both.