Service manual for Family FESM-550C servo motor?

[gosierra]

Hello Folks,

Just joined the forum. Thank you for this wonderful website. I can tell, I will be spending a lot of time on it. Hopefully, not so much as it takes away from my hobby!

I just purchased a used Juki 1541s with a Family FESM-550C servo motor. I'm having difficulty adjusting the speed using the dial on the motor.

The motor has a switch for clockwise, counter-clockwise, and center. It also has a dial indicating 0, 500, 800, ..., 3500. I can't find any other switches or dials on the motor. I assume the dial is used to set the maximum motor rotation speed. Is this correct?

I rotate the dial, but the foot pedal engages the motor at the same location and the max speed doesn't seem to change.

I disassembled the motor housing and disconnected the dial. The resistance changes as I rotate the dial, so the dial (a potentiometer) seems to be working correctly.

Perhaps, I'm not changing the speed correctly? I've always had a clutch motor. Sorry for the dumb question.

thanks,

Mike 

(Berkeley, CA)

 

 

 

[Northmount]

On 4/17/2020 at 7:06 PM, gosierra said:

It also has a dial indicating 0, 500, 800, ..., 3500. I can't find any other switches or dials on the motor. I assume the dial is used to set the maximum motor rotation speed. Is this correct?

I rotate the dial, but the foot pedal engages the motor at the same location and the max speed doesn't seem to change.

The dial should change the max speed.  It of course does not alter the foot pedal action.  If there is no noticeable change in speed with the potentiometer, then there is an electrical circuit problem.  (Start with the dial at high speed while the machine is running, pedal to the metal, with no thread in the needle, and turn it down.  You should see/hear the difference.  If you are running the motor only, you may not see/hear the difference.  Might need a tachometer to see.  Also speed will likely vary inversely to the load, so make sure there is some load on it.) 

Did you buy from a dealer or privately?  If you bought from a dealer, go back to him for support.

If a private sale, still need to go back to the seller and negotiate a fix or replacement.  Else you will have to find an actual circuit diagram and trouble shoot yourself, or replace it.

Tom