Please count the number of beeps before it stops and starts back, or if you don t feel doing that, follow this. Sorry to say this will be a fairly lengthy test. What you need to do first of all is boot up your computer with:
NO sticks of memory (RAM)
NO hard disks / storage devices
NO peripheral cards on (PCI-E/PCI/AGP/etc), that means no video card too if you're not using an on-board one
Literally just CPU and motherboard connected to the PSU
You must also disconnect the power supply cables form hard disks / storage devices, as a PSU will cut off power if a peripheral component like this has a short circuit happening. Ensure data cables are also disconnected.