I'll start by apologizing for asking another question on a topic which obviously pops up over and over and over again. I tried to locate an existing answer matching my situation, but I did not. If you know of an existing question/answer, please point me towards it.
I have two Intel DG45ID motherboards which failed to power up with minimal components installed when I use my Corsair CX430 430w power supply. By "minimal components I mean only the CPU & 1 stick of DRAM & the PSU were installed. When I switched on the Corsair PSU both the processor fan and the PSU fan spun for a few seconds and then they both stopped. No beeps from the on-mobo speaker. The power switch has no effect.
I have tested the PSU using this Rosewill Power Supply Tester and the tester thinks everything is copacetic.
Because the tester was happy it wasn't until the second motherboard failed to power up in exactly the same way as the original that I decided to try another power supply. After I swapped the Corsair PSU for an Antec Earthwatts EA-380 380w PSU, the motherboard powered up OK. (I haven't tested a complete boot yet, but the fans spin up and mobo beeps at me ... presumably because I don't have any input/output devices connected yet.)
Corsair's instructions for testing their PSU seem to boil down to connecting a case fan via a molex connector then shorting the green and black pins on the 24-pin connector and see if the fan spins up. Because I seem to find shorting two connectors too challenging, I changed this to connecting a case fan via a molex and then connecting the 24 pin PSU connector to the PSU tester. Both the case fan and PSU fan spun up fine and, once again, the tester was happy with the voltages.
Yet there must be something wrong someplace since the mobo won't power up unless I use a different PSU.
Is it possible for a PSU to have failed and yet still test as OK? How can this be?
It wasn't until after posting that I noticed the question New Power Supply doesn't work with a specific motherboard in the "Related" questions list on the right hand side of this page. My reading of the question is that the poster also had a CX430 fail with a specific, though different from mine, motherboard. Hmmmmm.