Originally Posted by sidgates

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My company was involved in servo manufacturing for 17 yrs (1968-1983). I was aware of all failures reported by customers and in house failures. We cycle tested every servo before shipment and there were a very few that failed in test. I remember one field failure and we found a grain of sand that locked the gear train. Another customer reported a servo reversed in the air and he landed with reversed elevator. My first reaction was this was impossible but later found Mitsumi had changed the way they anchored the magnets in the servo motor and the magnet came loose and rotated 180 degrees under vibration.

I feel vibration is the main cause of servo failure today. If a power connection or signal wire connection breaks the servo is going to be dead. If a pot connection breaks the servo is probably going to drive full travel. I suspect that most servo amplifier failures are caused by over voltage or prolonged high loads from mechanical linkage.


I have been flying R/C models since 1952 and have never personally had a servo failure in the air.