I think we've got one of these at the shop. Novak spent more time playing with it, I'll see if he's got any notes on the thing.
I didn't really look for fan control, I pretty much just switched it on and played with voltage adjust.
B2 to 5v via potentiometer = voltage increase
C4 to 5v via potentiometer = voltage increase
C2 to 5v = voltage increase
Here's the pinout reference I found and everything I checked on it seems to be correct- but it has no fan speed control.
http://static.rcgroups.net/forums/attachments/3/1/3/5/4/3/a4644398-12-Dell%20Poweredge%202100w%20pinout.jpg?d=1329627059I can double check but for some reason I was thinking the fan went on full speed when the supply is first powered on but slowed after a second or so (at basically zero load). If that's the case we might have slightly different supplies or possibly yours has a bad temperature sensor or something.
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novak