I've found many resources on the Internet on how to drive a small two-wire brushless fan and to vary its speed. What I didn't manage to find is information on the requirements for the power supply, besides what's usually on its datasheet.
In particular, I'd like to know what are the risks, if any, of powering it using a very simple AC/DC unregulated power supply (i.e. transformer, diode bridge, filter capacitor).
Could the electronics inside the fan, e.g. the controller, misbehave if the power supply is not properly regulated (of course, assuming the unregulated supply voltage output doesn't violate the maximum required by the fan)?
The reason behind my question is that I'd like to use some of those cheap PC fans that can be purchased on Amazon or E-bay to build a ventilation mechanism to blow away soldering fumes, and I'd like to keep the power supply as simple as possible (I plan to reuse some old unregulated wall warts I've in my junk box).