Asus ROG G75 won't stay powered on and no POST

adi_puscoi

Prominent
Jan 31, 2018
2
0
510
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! :wahoo:

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! :pfff:

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.
 
Solution
So, it's not the BIOS that is faulty, you have a component that after about ten seconds becomes defective, the only way to find it, is to take voltage readings to locate the problem.

Thank you for the input.

Managed to get a chip programmer and flashed a new bios image. It made things better; got to see the ROG logo and it even tried to boot off the HDD 😀. Also before powering off the screen doesn't seem to freeze anymore. However the power offs still occur and power on behavior is still unpredictable. 🙁

After flashing the bios and turning it on a few times, I left it over night with the battery and AC in to charge. In the morning came back to it and noted the power on states:
1st attempt - time until power off: 35 sec - display: turned on after 15 sec, black - fans: off
2nd attempt - time until power off: 4 minutes (manually powerded it off since nothing was happening and had to leave soon) - display: no - fans: start up at 47 sec at moderate pace
3rd attempt - same as 2nd
4th attempt - time until power off: 6 sec - display: ROG logo - fans: moderate
5th attempt - time until power off: 15 sec - display: off - fans: off
6th attempt - time until power off: 12 sec - display: off - fans: light - bonus: after powering off, it powered back on for like 4 sec with the ROG logo showing

Left it alone while I made tea and then returned and did a hard reset.

7th attempt - time until power off: 20 sec - display: turns on after 10 sec, ROG logo; reach Windows loading screen - fans: off
8th attempt - time until power off: 17 sec - display: turns on after 16 sec, black - fans: off
9th attempt - time until power off: 14 sec - display: turns on immediately, ROG logo and then Windows - fans: off
10th attempt - same as 9th
11th attempt - time until power off: 11 sec - other details same as 9th
12th attempt - time until power off: 11 sec - display: turns on after 10 sec, black - fans: off
13th attempt - time until power off: 13 sec - display: turns on after 8 sec, ROG logo - fans: off
14th attempt - time until power off: 5 sec - display: turns on immediately, ROG logo - fans: off

The declining time it stays powered on still makes me think of overheating, but the 2 attempts where it stayed on for longer and the general chaotic behavior make that unlikely to be the cause.

I may try to flash another image, but they are not that easy to come by in the full 8MB version (lots of dead links).