3 Module Power Supply not Boot Because 1 Module Fail

Hi, I've got a couple of older servers that wouldn't boot. Playing around with the power supply finds that one module in each server was bad. Which kind of defeats the purpose of redundant power supplies!

This is a 3 module 650W Power Supply - Emacs R3G-6650P.

The modules are GIN-6350P.

With the bad one identified and removed the server boots up fine but with the bad one added to the array of three it won't turn on, it just beeps once. I've put good ones in the slot where the bad one was and it still boots with the two good ones.

Is this normal behavior? I was always under the impression that if one was bad that the server would power up or keep going no matter what because its still got two good modules.

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andyalderSaggar maker's framemakerCommented:
It should work with a faulty PSU in one of the slots but the electronics is hard to design for redundancy. Suppose the output of one PSU is short circuited, it will pull the outputs of the other two down as well. See this HP advisory for example - http://h20564.www2.hp.com/hpsc/doc/public/display?docId=emr_na-c01519680

You can design out the short-circuit of one PSU by having fuses on the PSU backplane but then the backplane becomes a SPOF.

I've also had a problem on one server with a faulty temperature sensor in a redundant PSU telling the server to shut down because it was too hot, two PSUs double the chance of that happening.

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