how to repair a servo?

[Bob Chiang]

Hi all,

I have a sub micro servo that doesn't function due to a crash. If I play with the pot wiper manually, I can get the gear train to move back and forth and stop. But left to its own, the motor and gears continue to run until I move the transmitter stick and then the motor and gears run continuously in the other direction.

Is the output gear supposed to be directly connected to the pot? This one has a firm (all relative for these tiny parts) press fit, but the pot shaft doesn't move when the output gear turns.

Any suggestions for how to fix it?
Shall I add a couple of limit switches and fly it like a reed servo? ;)

[Markz]

Hi Bob,

Based on your explanation, it seems that the electronics are fine, but the mechanical gear drive is not. This is a common failure for this type of servo. The output shaft and the pot are directly connected - the pot is feeding back the position of the output shat to the control board. Somewhat your servo lost that mechanical connection.

Depending on the brand of servo, gear trains are generally easy to find and affordable. If there's no missing teeth on any of the gears, you could potentially glue the output gear to the pot, but that will prevent you from being able to replace the gears.

Marc