The computer is dead and does not turn on - where to dig?

Question

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Dead computer. At startup, something turns on, there is no picture, then it turns off and turns on again ... And so on endlessly. Tell me where to dig? Nothing squeaks, just the fan rustles

UPD: started!

Answer 1

Try to clean the dust first. Then reset the BIOS (there is a jumper on the board, or get the battery). Speaker not beeping? If it beeps, you can find out the fault code by the signal. Well, then see if there are any traces of "fires".

Answer 2

another option is to disconnect everything from the mother (hard drive, all expansion boards, “play” with memory) try to run it. If it starts, then connect the disconnected one at a time and test for launch.

Answer 3

If the fans do not start, then either the PSU or the motherboard, and rather the first one.