Readynas 4200 v2 Power Supply Fans Not Turning Off OS6

Mine are off when the unit is, but I believe there is circuitry in the power supply that turns the fan on if it's too hot (or the thermal sensor says it is).  It's still producing the 5 volt standby and possibly other (I just don't know on the rack-mount units) voltages and that part of the supply could fail if it gets too hot.  Mine are actually often off when the unit is on, as the main fans apparently provide enough cooling.

I don't know if Netgear used different models of power supply in the unit.  Since the 4200V2 is a modified SuperMicro system, supplies are readily available, and quite cheap on eBay.  The newest ones have a fan that runs a lot quieter and is definately off much of the time.