The encoder cable carries highly sensitive low-voltage signals. Any damage, stretching, or loose connection in the cable run from the motor back to the servo amplifier will scramble the pulse data.
When the FANUC 366 alarm occurs, you may notice the following symptoms:
Even if it looks fine, replace the cable as a cheap and fast diagnostic step.
Would you like a specific diagnostic flow chart or parameter list for your FANUC controller model? fanuc 366 alarm
The encoder itself can fail internally. This might be due to a failed internal circuit board, a damaged glass scale/disk inside the encoder casing, or general wear and tear from years of high-speed operation. 4. Servo Amplifier or Control Board Failure
A very specific question!
Unplug the encoder cable at both the motor and the servo drive. Check for bent pins, moisture, or metallic debris. Clean with electrical contact cleaner and firmly plug them back in, ensuring the locking rings or screws are fully tightened. Step 2: Check for Electrical Interference (EMI) Would you like a specific diagnostic flow chart
The feedback cable connecting the motor to the servo amplifier is damaged, frayed, or experiencing electromagnetic interference (EMI). Loose connectors at either end can also drop signal strength.
If you do not have a backup, do not clear the PMC. The machine will become a brick.
The machine builder used a SUB 23 (ROT) instruction (rotary table calculation) inside a Level 1 PMC rung. Every time the spindle encoder sent a pulse, the ROT instruction recalculated the entire position matrix. Inspect the pins for bent components
Disconnect the encoder cable from both the motor end and the servo amplifier end. Inspect the pins for bent components, rust, or moisture.
To resolve the SV0366 alarm, follow these diagnostic procedures: