My desktop was working normally before I stopped using it for about a month during exams. It was covered while sitting unused, and now pressing the power button produces no response at all: no fans, LEDs, beeps, or other signs of life. The monitor powers on normally but reports no signal because the computer never starts. I've already checked the wall outlet and power cable, and I don't see any obvious damage or burn marks inside the case. What should I test first to determine whether the problem is the PSU, power button, or motherboard?
2 Answers
A paperclip test can be used as an initial PSU check by bridging the appropriate power-on pins on the main connector, but it’s only a basic test. It may show whether the unit starts at all, but it won’t confirm that every rail has the correct voltage or that the PSU works properly under load. Be especially careful with proprietary systems from manufacturers such as Dell, HP, or ASUS, since their connectors and pinouts may differ from standard ATX wiring.
Start with the basics on the PSU itself. Many power supplies have a rocker switch on the rear that can get bumped, although some systems or proprietary power supplies don’t include one. If yours has no switch, move on to testing the PSU and the case power-button circuit.

I checked the back and this power supply doesn’t have a power switch.