WHY DO I NEED A SERVO SHOP?
Can I repair my own servo motor? How about the motor shop down the street?
Before you try to repair your own servo motor or send it to your average electric motor shop you should know that servos have distinctive components that require specialized care.
DC servo motors use tachometers for feedback. Tachometers are like a small DC generator that the servo drive uses to monitor the servo motor's speed. You can test the tachometer's output with a voltmeter but the DC signal is as important as the voltage. An oscilloscope is needed to see the quality of the signal and to be sure it is not too noisy. A noisy signal can confuse the drive and cause the servo motor to run improperly.
AC servo motors can have a variety of feedback devices. Some will have a resolver, tach hall device, or an encoder. Some units can have a combination of the three. If your shop can't test these devices, read the various signals they output, or properly align them to the servo motor then they can't be sure the unit will function properly in your machine. Taking a chance that the feedback devices are okay without proper testing will usually lead to having to pull the servo out of your machine and starting over again. Avoid this scenario by sending your servo motor to a specialized servo repair shop who has the means to properly service all of their parts.
AC and DC servo motors both have permanent magnets inside. These magnets can weaken when the unit is disassembled. If your shop does not have the means to recharge these magnets, then even attempting to repair the servo motor may cause it to function improperly. Recharging the magnets found in servo motors requires a magnetizer; a piece of equipment that many shops that claim to repair servo motors either do not have or do not have the expertise to use for recharging servo motor magnets.