Power Problem in PC
My PC was running fine, then suddenly It just Got hanged on task manager was working at that time, but I it is also seems to be stuck so I decided to restart the PC from power button, After that, It didn't turn on, I tried many times pressing the button on the case, and suddenly its turned on, then by chance the power cable got disconnected from the electricity board. I reconnect it and since then it is not working, I checked electricity is in mother board. The power supply box is also fine. Any help ? where can I start the pc from motherboard. It's an intel 8502 or intel 810 Don't exactly know, But it's quite old pentium III that has 24bit colors
When you say electricity board, do you mean the big board inside the case that everything plugs into? This is the motherboard, just need to keep the terminology correct.
Assuming this is the case, how do you know it's still powered? It can hold a charge for a while even when completely disconnected...some LEDs stay on. To check this, disconnect the PSU from it and hit the power button...it'll discharge any residual electricity. Plug your PSU back in and hit the power button...do the motherboard LEDs light up, fans start spinning etc?
If you have access to another PSU, then try that too...there are no guarantees your existing PSU is fine like you say, the fault may be intermittent. You can buy a box that will start the motherboard without needing the case power button, or if you have access to another case you can connect your system to that and use the power button on the second case.
From how I've read your post, it sounds like an electrical fault on the motherboard...the case power button is probably fine. But you'll need to check everything step-by-step which may take a bit of time.