Mitsubishi Electric MELSERVO-J4 Series Transition Handbook page 106

Part 3: Review on Replacement of MR-J3-_B_ with MR-J4-_B_
(4) For separate repair (Note)
Replacement of Servo amplifier (MR-J3-_B_)
SSCNET III servo system controller
MR-J3-_B_
J3 series servo motor
● J3 series servo motor driving with MR-J4-_B_ servo amplifiers
(J3 compatibility mode) will be sequentially available.
Check "Part 7: Common Reference Material" for target motors.
Note. Separate repair means replacement.
MR-J3-_B_
MR-J4-_B_
(J3 compatibility mode)
J3 series servo motor
3 - 5
Replacement of J3
SSCNET III servo system controller
MR-J3-_B_
J3 series servo motor
● The J4 series servo motor cannot be driven by the MR-J3-_B_
servo amplifier. Replace the existing servo amplifier and servo
motor with MR-J4-_B_ servo amplifier (J3 compatibility mode)
and J4 series servo motor simultaneously.
series servo motor (HC/HA)
MR-J3-_B_
MR-J4-_B_
(J3 compatibility mode)
J4 series servo motor