This motor and its drive circuit are one unit (the circuit board is on the end of the motor opposite the impeller, in the air stream):
It seems to me that the element in the lower right corner (RT1696) is a thermistor, or such. This is what controls the motor speed?
The manual this is from describes the thermistor (RT1696) as:
RES.,THERMAL:5 K OHM,10 PERCENT
No generic pn is given. It is a little green teardrop with a red dot on top.
If I want to boost the minimum speed, or alternatively, push the entire speed range up by a few hundred rpm, do I add an adjustment pot in series with RT1696?