I left the cover off a tower PC and walked away while it installed linux (yes, bad idea). The cover had the cpu fan mounted on it but the CPU also had a fan strapped on it. I don’t know if the CPU-mounted fan was running or if the machine was entirely dependent on the cover-mounted fan directly above the cpu.
Someone junked this PC (asus p5b) simply because it’s old (2007). Seems like a high-end gaming machine designed for overclocking. Strangely, when I returned to the machine to find it powered off, I felt the heatsink and it did not feel warm at all. Power supply is apparently fine because a green LED on the motherboard is lit. When I press the power-on button the HDD LED flashes for a split second but nothing happens.
I thought if CPUs get too hot there is a protection mechanism to force a power off. Was that the case in 2007? The manual mentions this:
CPU TM function [Enabled] Allows you to enable or disable the CPU internal thermal control function. In TM mode, the CPU power consumption is reduced. Configuration options: [Disabled] [Enabled]
Would that setting cause a protective shutdown? I don’t know how that was set.
Posting this SO before my reply: https://superuser.com/questions/1571472/pc-wont-turn-on-short-flash-of-light-and-then-nothing
Also Reddit post that might be helpful: https://www.reddit.com/r/NZXT/comments/q3fxxx/pc_wont_even_turn_on_just_keeps_flashing_like/
I’m a bit confused as to the exact issue and I can’t really picture this right now, but try taking out everything and unplug the psu as well. What I mean by taking out everything, I mean also including the cpu. After it is all out, put in everything one by one starting with the psu. For ram check if there is a specific order you have to put them in (Yes this is a thing and I had to do this when upgrading my ram on my dell precision). Whenever you are testing one by one, pay attention to any noise or led lights. Machines usually either blink a pattern or make a noise of kind of like a morse code. This is very helpful with figuring out the issue since the lights and noise are actually error codes that can be looked up. Put the harddrive last and the cpu second to last this way we can try to eliminate any other issue. If everything including the CPU seems good, check the cables and reapply the thermal paste to the CPU. Also if you have another PSU lying around try switching them out.
Also check if the HDMI is plugged in and the monitor is on before doing all this. I know it is a bit condescending but trying not to be. Sometimes it is something simple.
EDIT: Try to check all the cables first and unplug and replug. Also try different outlets and whatnot.