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HP EX475 Power supply connector

I have an HP EX475 mediasmart server which has just blown its second power supply. The PSUs always fail when MY UPS kicks in (I know this now!!) Whilst I look around for a replacement from another manufacturer I thought I'd use another PSU to get the server running again. I found a redundant PC PSU with an 20 pin ATX connector (it even had P1 stamped on it the same) I was just about to plug this in when something made me check the wiring. The old PSU and this PC one seem to be wired differently. I have buzzed things through and they do indeed seem to be different. The PC PSU complies with the ATX standard that I can find all over the net. The blown HP supply is different. How can this be? Surely a standard is a standard - it makes me concerned about getting a replacement that is wired correctly.

Any body else got any experience or advice?

Mark Preston
Mark Preston
1 Solution
Non TRUE sine-wave UPS units will kill PSU's that use PFC.
It's less of a problem if you are on 115v (vice 220v) power but can still happen.
It's more of a problem with Active PFC than with Passive.

The reason is when PFC tries to Power Factor Correct a stepped square wave (simulated sine-wave) it kicks the input voltage to the PSU to a higher voltage than the input filter caps (and sometimes rectifier diodes) are rated for.

Less expensive UPS units are not true sine-wave models.

Mark PrestonSystems EngineerAuthor Commented:
I am really quite annoyed at HP over this.

It is a SERVER and needs to be available so it's stupid that it won't run on an ordinary UPS.

OK, so you build a server than won't run on a UPS and you don't tell anybody. We all have to find out by blowing up power supplies.

Then when the inevitable happens you can't even do a stop gap by using another power supply because for some crazy reason you have non standard wiring for the power supply connector.

Talk about making things easy - it's a catalogue of disasters.

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