FANUC A20B-8200-0143 is a servo motor feedback encoder that reports rotor position and speed to a compatible FANUC servo system. It is a motor-mounted encoder assembly, not a CNC main board, robot controller PCB or servo amplifier.

A confirmed application is the FANUC A06B-0115-B275#0021 βiS 0.5/4000 AC servo motor. Available documentation identifies this motor with a brake, keyed straight shaft and incremental feedback. Compatibility must be checked from the complete motor and encoder nameplates.

A20B-8200-0143 Product Information

Servo Position and Speed Feedback

The A20B-8200-0143 converts motor rotation into feedback signals used by the servo amplifier for closed-loop control. Stable feedback helps regulate speed, position and torque response. Encoder faults may cause feedback alarms, unstable motion, vibration, positioning errors or failure to enable the servo axis.

Exact Motor and Encoder Matching

Do not select this encoder from the A06B-0115 family prefix alone. Confirm A20B-8200-0143, the full motor number including #0021, connector, mounting, feedback specification and amplifier compatibility. Other A06B-0115-B275 suffixes can use different detectors and are not automatically interchangeable.

Testing and Installation Notes

REACO CNC checks the marking, housing, connector, electronics, feedback signals and pulse consistency with a compatible motor or test setup. Replacement requires correct mechanical alignment and feedback phasing. Qualified personnel should verify parameters and complete the required machine reference procedure after installation.

Related resources: FANUC CNC and servo parts and FANUC servo motor and encoder repair service.