Old PC starts and shutdown randomly within 2 seconds to 1 hour

[amish]

So as I have been discussing in some other thread. I am planning to purchase new PC.

But before that I am just testing the old PC which I almost NEVER used. (harddisk used only for 45 hours in total)

I started this PC after like 8-9 years. But it looks completely brand new.

It has 3 fans in total. CPU Fan, Cabinet fan and PSU fan.

Here is what happens - randomly:

1. I press power button, all fans start and switch off in 2-3 seconds (without beep sound)
2. I press power button, all fans start and switch off after 5-10 seconds (after beep sound)
3. I press power button, all fans start and OS boots (and then switches off from 2 mins to 1 hour)
4. After switching off, it does not restart by pressing power button OR pressing reset button
5. To restart either I have to turn off/on wall switch OR press power button for 7-8 seconds, release it and then press it again.

I was able to install Linux yesterday and then it stayed on for almost 1 hours (or may be little less) and then switched off directly.

I believe it is SMPS problem but just wanted to ask if there could be any other reason, like motherboard going bad etc.?

Thank you.

Photos attached - in case someone wants to have a look.

 

[socrates]

Deleted - repetition

 

[Smh]

@amish did you found any solution?

 

[JitzyJT]

check if the shutdown switch is rigged

 

[amish]

@Smh - I took it to repair center and they changed some chip on motherboard.

I tested it for 1 day. Then got busy with other things and old PC is just sitting there unused.

I plan to restart it soon.