In a previous TechNote, repair of worn fan bearings was covered. In this follow-up article, we consider what to do when fan drive electronics fail.
Mechanical maintenance of fans is usually all that needs to be done. However, occasionally, an electronics failure occurs. In the fan shown in the previous article, the tan-colored, stator-mounted etched-circuit-board (ECB) can be seen (in the second rotor removal picture) to have four components mounted on it: two 22 μF electrolytic capacitors, one 1N4007 diode, and a four-terminal IC that was positioned so that the rotor magnets could activate the Hall-effect device (HED) inside it. In the above fan, this component seemed to have failed. (The others tested good.) Rather than attempt to obtain a replacement for an obscure, probably foreign-made part, I decided to design my own motor-drive, one that I could maintain in the future. Most products have room for a small drive board and the original fan terminal connection provides power for the drive.
