Three of these fans: Nidec TA150CD C34957-58 40 x 28
in a 1U rackmount server failed after a customer hot-unplugged and re-plugged each one in an attempt to determine which one was noisy. =20 Now, none of them work even when conencted to a different system. =20
A 4th, thinner model of the same fan survived, and works if connected to any of the failed fans' connectors. It continues to run even after many hot connect cycles. =20
In the support center, we tried the same thing on a lab system, and the same three fans died there as well. Also, the connectors are keyed, so it would be extremely difficult to connect them backwards, and it's unlikely that two different people would have made the same mistake.
They are speed controlled, but I don't know if it's analog or PWM. One theory is that the open circuit voltage floats above 12V, but the highest voltage from the power supply is 12V, and I doubt they'd do any step-up tricks just to run 12V fans. (I'll confirm when I get a meter on the supply pins tomorrow.) =20
Any thoughts on this one? =20
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