This is the resistor or transformer unit, the fan plus in here and there are 6 relays that form a cobination of voltages either from the restor unit (this is two 5 inch long tubes on top of the unit) or the transformer type (much better) which has a larg transformer and the relays on the other end.
What happens is that some relays bur out and yo get dead spots as the voltage climbs, also as the highest speed is when the most current is drawn then this always burns out. If you want any other help then reply bill@kidsathart.co.uk
Bill hartmann
January 2009