RE: [CAD_CAM_EDM_DRO] Interesting Servo Motor Encoder Problem

I recently came across an interesting servo motor encoder problem. I had
installed an Us digital encoder onto a servo motor and after centering
the code wheel and installing the Agilent read head I tested the servo
motor and encoder on one of my older Gecko G320 servo amps. When I
powered up the servo amp the motor took off running at very high speed
then gradually slowed down. When it stopped the motor had no torque and
then faulted out. I rechecked all the connections and motor/encoder
polarity and everything was fine. I connected the motor to a separate
power supply and it ran fine. So I knew the problem was either in the
old gecko or the encoder. I changed the motor out with another motor
with the same type of encoder. It ran perfect and the encoder worked
perfect. Now I knew that the G320 was good. Then I took apart the
encoder on the dective unit and reassembled it again verifying that the
wheel was running true was the proper height and that it was
mechanically centered to the read head. Everything was perfect but upon
retest the same high speed start was noted and loss of torque. So I
trundled out to my shop took apart the encoder for the third time
reinspected everything and concluded that it had to be the read head was
bad. After verification that indeed the correct read head was supplied I
replaced the read head with a different one and reassembled. This time
it ran perfectly tracking just like it was supposed to.
So this is probably a rare problem because I have probably installed
several hundred of these read heads and never found a bad one. What was
really weird was that something internal to the encoder read head must
have been acting like a pulse generator to cause the motor to spin and
then slow down.
Having fun
Dan