Hi, I've built quite a few computers and troubleshooted a good amount of hardware issues, but this one is new to me. When I power on my computer, I get a burst of life from the GPU fan, the case fans, and the power-on LED, which then all simultaneously cut out about 2 seconds later. The odd part is, then it will continue to restart and die at about 3 second intervals until I cut the PSU switch off, except except for one last click even after the PSU switch is off. No POST, no beep codes, nothing. At first, I thought the power switch plugs simply got loosened somehow, as it seemed as if the power switch was continually shorting.
The conditions leading up to this are thus: I just took off the stock CPU cooler and threw on a Tuniq 120 tower. Now, as I said I've done this stuff plenty of times so I don't THINK I screwed anything up in doing this (the install required pulling the whole mobo out and attacking a bracket to the underside).
Additionally, just after installing it, the comp started up just fine, and I ran it for about 10 minutes with no problems. I ran a variety of programs (SpeedFan, CPU-Z, ATI Omega control panel) to verify that the CPU was running fine and not overheating; a steady 30C. Then, realizing I had forgotten to reconnect my front side USB and sound, I turned it off, and immediately this restarting problem began.
The measures I have taken in attempting to diagnose this:
Waiting, trying again
Checking connections, particularly power switch
Pulling all components down to the CPU and replacing them one at a time
Disconnecting mobo power, reconnecting, etc
All to no effect. I am terrified that I somehow burned out the CPU or mobo, but I don't see how that could be the case since it started and everything was just fine, especially CPU temps, and it didn't cut out forcibly; I shut it off myself. My guess/hope is that perhaps the PSU cut out, and the timing is just a coincidence? This isn't at all like dead PSU's I've had in the past, and does smack to me of a dead mobo.
My components are as follows (computer is just over 6 months old):
2 GB Corsair DDR800
ATI Radeon x1900
Thanks in advance for your help.