On and off, on and off

[Talk2Me]

I have a computer that the power supply will turn on, the fan begins to go, then it shuts off. Waits. Then does it all over again, and again, and again. It never boots. SO I put a new power supply it in. Same problem. Any suggestions?

[kiosk]

-CPU heatsink or thermal compound not doing their jobs.

-Mainboard failure (capacitors gone open circuit or CMOS battery drained)

-Excessive current drain somewhere in the system (something shorting against the back of the mainboard, possibly current-leaking capacitors which have failed due to dielectric breakage)

[Whyzman]

Capacitors

http://www.pcguide.com/vb/showthread.php?t=25482

[1966]

Curious, but how old is your system? Fairly current?

[CoachB22]

Stuck case switch?