Roland Jupiter-4 (JP-4) – Battery Replacement (CR2032)

In this video I will be replacing the original NiCad battery in a Roland Jupiter-4 (JP-4). This kind of battery is prone to leaking which can cause problems. In the JP-4 this is not an very big issue (at least compared to e.g. Korg Polysix where the leaking battery will cause havoc and damage traces and chips) as the battery is mounted away from the circuit boards.

I replaced the original battery with a CR2032 battery in a holder. Please note that the original battery is rechargeable and this is not. I remove the R2 and R3 resistors to prevent charging of this battery. The battery is only used to keep the RAM chip alive while when the power is switched off. This battery does not have the same voltage as the original one but this is OK as the RAM chip requires very little voltage to “stay awake”.

In the video I use a CR2032 holder which is intended for mounting on a PCB, this is not ideal as I mount it with double sided tape. I would have prefered to use e.g. an Adafruit Sewable CR2032 Holder as these are completely flat and have the “pins” on the side. I could not get one of these locally in a shop in Gothenburg, Sweden (they have been available earlier).

To figure out which resistors to remove to disable the charging I consulted the service manual but I also found this link: http://www.retrosound.de/The_Jupiter-4.htm

PLEASE! If you are going to do this; DISCONNECT the unit from mains power! You should always do this but in this case you will be working VERY close to to the unprotected power supply

Original battery (yellow) mounted in its bracket

CR2032 mounted onto the original cable
From the service manual (I’ve added the red sequare) – We have to remove R2 and R3 to disable the charging circuit
CR2032 Battery Installed – Note that R2 & R3 have been removed!

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