Mitsubishi Electric no longer makes or repairs MR-J2S or MR-J3 servo amplifiers. Its own legacy pages name the MR-J4 family and its HG motors as the replacement. That is the right answer for a planned retrofit; for a machine that is down tonight, a like-for-like MR-J2S or MR-J3 spare is often the faster one.
Where the two series stand
Mitsubishi Electric’s US legacy-product pages give the dates:
- MR-J2S: introduced in 1999, discontinued in 2015. Repair service ended in August 2022.
- MR-J3: introduced in 2003, discontinued in 2019. Repair was offered until May 2026 or until repair parts ran out.
For both, the same pages name the MR-J4 servo family with compatible HG motors as “the most suitable replacements”.
The official way forward: MR-J4
The step from MR-J3 is the shorter one. Mitsubishi Electric’s MR-J4 product pages say the MR-J4-A and MR-J4-B share mounting dimensions with the MR-J3-A and MR-J3-B. A J3 compatibility mode lets an MR-J4 amplifier run on an MR-J3 system without changing the controller, though some functions are unavailable in that mode.
From MR-J2S the step is larger, and Mitsubishi’s migration manuals list what changes: wiring, parameters, the network and, often, the motor. Finding a replacement part walks through what to compare before you commit.
When a like-for-like spare is the better choice
A retrofit is engineering work: a new amplifier, often a new motor, parameters converted and tested on the machine. When the fault is one amplifier on a machine that otherwise runs, and the plan is to keep it a few more years, a used, refurbished or surplus unit of the same model is usually quicker and cheaper. Many plants do both: a like-for-like spare to restart now, the MR-J4 migration planned for the next shutdown.
Searching Sparehawk for these series
Search by the series prefix on the rating plate. For these two servo generations and their neighbours, that means:
- MR-J2S amplifiers, and MR-J2, the generation before
- MR-J3 amplifiers
- MR-J4 amplifiers, the successor
- HC-KFS, HC-MFS, HC-SFS and HC-UFS motors
- HF-series and HG-series motors
Each offer shows its condition (New / OEM, new surplus, refurbished or used), the supplier’s country and the lead time. Search MR-J2S, MR-J3 or browse all Mitsubishi Electric parts.
Before you order
- Copy the full model from the amplifier’s rating plate. The letters after the rating (A, B, the -RJ or -PX suffixes, a special code such as -S100) change the interface and the function, and a unit with a different suffix may not talk to your controller.
- Match the motor and the amplifier. Note the motor model and its encoder; a replacement amplifier has to drive the motor you already have.
- Save the parameters first if the old amplifier still powers up, with MR Configurator or MT Works. A spare arrives with its previous machine’s settings or with the factory defaults.
- Ask what “refurbished” included. For amplifiers of this age, capacitors and fans are what fail. Refurbished, surplus and used explains the conditions, and warranty on surplus parts lists the questions to ask about cover.
If no offer matches the model you need, send a request with the rating-plate photo: how requests work.