Mitsubishi MR-J4 AL.16: Encoder initial comm error 1, what to check first?
I'm getting an AL.16 alarm on my Mitsubishi MR-J4 servo amplifier right at power-up. This started after we replaced the motor and encoder cable. What should I check first?
Alarm AL.16 on a Mitsubishi MR-J4 servo amplifier indicates an Encoder initial communication error 1. This means an error occurred during the initial communication between the encoder and the servo amplifier, typically at power-up or after component replacement. The detail number can provide more specific information about the failure.
Likely causes and checks
1Encoder cable disconnected, open or shorted
- Points to it
- This is the most common cause, especially if the alarm appears at every power-up or after the cable was recently moved or replaced.
- Check
- With power off, inspect the encoder cable for any disconnections, open circuits, or shorts. Repair or replace the cable as necessary.
2Wrong encoder cable communication method setting
- Points to it
- Incorrect settings for two-wire or four-wire communication can prevent initial communication, often indicated by detail 16.3 after commissioning or a cable change.
- Check
- Check the parameter setting for the encoder cable communication method: [Pr. PC22] for MR-J4-_A_ amplifiers, or [Pr. PC04] for -B, -WB, -RJ010, and -GF amplifiers.
3Unused axis not disabled (MR-J4W multi-axis)
- Points to it
- On multi-axis MR-J4W units, an unused axis that is not properly disabled can trigger this alarm, often with detail 16.3 on an axis without a connected motor.
- Check
- If using an MR-J4W multi-axis amplifier, ensure any unused axes are disabled using the disabling control axis switches (SW2-2/SW2-3/SW2-4).
4Unstable control circuit power supply
- Points to it
- Brief dips in the control power supply can disrupt initial communication, often accompanied by detail 16.3.
- Check
- Monitor the control circuit power supply voltage for any instantaneous power failures or instability.
Next check: After checking the encoder cable, verify the communication method setting in the amplifier parameters. If the issue persists, especially on a multi-axis unit, ensure all unused axes are properly disabled.
Related questions
Describe the fault or upload a photo, and InduQT checks it against the manufacturer manuals. Share the result here when it helps someone else.