Hopefully, the smiley is not directed against me. The power supply is there already suspect, but it may be that the push to turn the housing is permanently damaged and shorts, then the PC goes after a few seconds even in the standby mode and is woken up again, etc. Can you do something on the motherboard? Therefore one must remove the wiring from the cabinet. Then you can bridge the two power pins with a screwdriver blade short, so get to the switch on the motherboard.