My computer don't start. How could I check if it the power source is out?

Switching power supplies, or using a PSU tester.

A lot of local computer shops will test a PSU for free if you bring it in, since it takes less than two minutes and it's a good way to get a potential customer in the door.

More info will give you more answers
Nevertheless If you switch on your system and theres absolutely no sounds,lights,power supply fan spinning than you know theres no power at all.in that case check your power supply cord inside the case and externally
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