Tough power supply problem

[sleepylight]

I have 4 Giga-byte K8N-Pro moether boards in rack cases. All the boards are in identical configurations. I bought 4 identical power supplies, hooked all of them up exactly the same, and only 1 boots. The 1 booting machine works whatever power supply is attached.

I figured this ment something was wrong with my boards until....

I took a completely unrelated power supply out of a P4. With that PS I'm able to boot _every_ machine. So I thought, maybe there's some wierd incompatibility. So, I got two more power supplies (for the two non-working computers) by swapping with other machines. All of the new PS's I swapped out work in the old computers, but the old power supplies are not working in the K8N boxes.

All the power supplies are at least 400 Watts, all have identical sets of connectors, and all test ok. When I connect everything and hit the power button on a combo that does not work the MB's power light flickers for an instant and the fans jerk once, but that's it. The onboard 'ram light' comes on and stays on just like it does anytime the board is powered correctly.

Has anyone else had this problem?

[Cricket]

What brand is the power supplies in question?

Cricket

[sleepylight]

The 4 identical ones that are giving me problems are made by realpowerpc.com. The one that seems to work on everything is made by antech. I swapped out 2 of the realpowerpc supplies with some from home in the hope that it was just a wierd incompatiblity. That didn't make any differnece though.

So, now I have:
1 Antech
1 RealPowerPC
1 PowMax
1 AOpen.

[Redfallon]

sounds like it could be insufficient voltage on the rails of the other psu's.....consistent voltage on all of the rails is more important than the total amount of watts, modern computer equiptment is very sensitive to voltage fluctuations....also some cheaper PSU's list the max wattage (400W or whatever) versus the RMS power....like the difference between peak and RMS on an amplifier.

[Cricket]

I never heard of RealPowerPC before, so don't know if it's good or not. I do know the PowMax isn't very good. The Antec and AOpen power supplies are good quality units.

Cricket