Well...... I finally replaced the internal lithium battery in my MKS‑70 and also in my JX‑10. I bought my MKS‑70 way, way back in 1987 and I've never had to replace the battery...... for 27+ years. I thought I would stay one step ahead of the game and replace the battery now before it leaks and causes any circuit board damage. I was dreading this project because I did not want to open up a can of worms. If you've ever looked inside of an MKS‑70, you'll know what I mean. I decided to install a battery holder at the same time so that future battery replacements will be easier. So...... the next replacement time will be when? The year 2042? I should mention that this is not a project for a novice. If you have little or no experience using a soldering iron, this is a really bad time to start learning. I recommend that you take your synthesizer to a Roland Authorized Service Center.

DAMAGE For those of you who have the new Vecoven SuperJX‑flash board installed, the backup battery is still required. Even though the new Vecoven SuperJX‑flash board uses updated EPROM technology to store banks of Patches and Tones, the currently selected flash bank is copied into RAM memory (which still uses the older 1980's technology) and is only written back to the Vecoven SuperJX‑flash board when a different bank is selected

I buy all of my coin cell batteries and holders from
The battery is a CR2450 Lithium Battery (Mouser P/N: 658‑CR2450)
       Note: This battery is larger than a standard CR2032 coin cell battery because is rated at nearly 3x the power (620 mAh vs. 225 mAh)

The battery holder I like to use is a Through‑Hole PCB Mount manufactured by Keystone Electronics (Mouser P/N: 534-1053-BH)

I recommend buying a name‑brand battery like Panasonic. Saving fifty cents to purchase an off‑brand is, in my opinion, a bad idea. This battery needs to last a very long time so get a quality one without the need to worry about a cheap‑o brand leaking and ruining your circuit board

Before you start, make sure you have saved all of your patches and tones to an external device such as a computer or an M‑64C cartridge

CR2450 Battery

* * * All of the internal patches and tones will be erased when the old battery is removed! * * *

Make sure you wear eye protection, are properly grounded and working on a static‑free workbench or table
* * * Please don't ignore the advice of eye protection, grounding and a static‑free area * * *
The chances of finding a new circuit board...... slim to none ;^)

The procedure is somewhat time consuming because of all the boards and cables inside. You will need to unplug, unscrew, and move a lot of things to gain access to the battery. The replacement took me about 90 minutes from start to finish. I was taking extra time and being extremely careful to avoid any ESD nightmares

(Refer to the images below)

1) Unplug the synthesizer!

2) For the MKS‑70 remove the top cover and locate the Assigner Board. It is buried underneath two Module Boards. You will need to unplug cables and move them out of the way. Both Module Boards are on hinges (I preferred to unscrew Module Board #2 and place it aside). For the JX‑10, remove the side panels and locate the Assigner Board

3) Unscrew the Assigner Board from the case and locate the battery

4) Once you locate the battery, you will notice it is soldered onto the circuit board
To remove the battery, use a small pair of sharp wire cutters and carefully cut the battery leads from the circuit board and then discard the battery.

5) After cutting the battery leads off, unsolder the leads left behind on the PCB and remove all excess solder from the holes on the circuit board*. Ensure the holes are large enough for the new leads on the battery holder

* Note that if you are using the Through‑Hole PCB Mount Battery Holder (Mouser P/N: 534‑1053‑BH), you will need to ensure that different holes (other than the original ones) are free of excess solder (see example image below). The new battery holder sits slightly off‑center from where the original battery was located. At first glance it looks odd, but don't worry. This new battery position does not interfere with any screws, boards or wires

6) Solder the new battery holder in place. You may need to slightly bend one of the battery holder pins to make it fit. Insert a new CR2450 battery and re‑assemble the boards and synthesizer case

7) When I turned the power on, the display showed a garbled mess of characters. Panic set in! This glitch I encountered was not really a glitch after all. Everything in RAM was erased when I removed the battery. Duh! All I had to do was "COPY CARTRIDGE TO INTERNAL MEMORY" and then everything was back to normal...... whew!

NOTE: Be sure to set SYSTEM EXCLUSIVE ON and save it because this setting will change to "OFF" (the factory default)

I think it's amazing the old battery lasted for 27+ years without leaking or showing errors on the display panel. Dodged a bullet!

MKS‑70 Cover Removal (upside down)
MKS-70 Cover Removal

MKS‑70 Battery Location (right‑side‑up)
MKS-70 Battery Location

MKS-70 Battery Location
Assigner Board Before - 1

Assigner Board Before - 2

Detailed Image After Battery Has Been Removed

Assigner Board Solder Free

New Battery Holder Soldered In Place

Assigner Board After
                            New Battery Inserted

Assigner Board New Battery

JX‑10 Panel Removal (upside down)
JX-10 Panel Removal

JX‑10 Battery Location (right‑side‑up)
JX-10 Battery Location

Safety Precautions:
Modifications made to any factory stock equipment will always pose an element of risk. Sometimes mistakes are made which are irreversible. Improper soldering and handling of electricity can cause serious injury and damage the synthesizer. Use caution when handling static sensitive devices and the PCB. Make sure you are properly grounded, working on a static‑free workbench or table and wearing eye protection during any soldering tasks. The author is not responsible for any damage or injury resulting from this DIY info. Use this DIY information at your own risk. And, I can't stress enough, the importance of wearing eye protection while soldering. That stuff flies everywhere sometimes!

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