JMP-1 Service - 230V to 120V Conversion and Battery Upgrade

I purchased an old JMP-1 unit from a seller in the U.S. who had at some point originally purchased this from Europe so it was setup to run on 230V. They even included the step-up transformer with the sale. The price was great and the conversion is a very simple process. I also remove the button cell battery from these amps and modify them to use two AA batteries that will be accessible without having to open the chassis. In a touring situation this reduces downtime considerably. My last modified JMP-1 had the battery last approximately 10 years and I travelled with it all over the world. When it was time to change it out my tech was able to do it without having to remove the preamp from my rack so we didn't lose valuable set up time on stage.

It is important to note that strange problems arise when the battery finally bites the dust. You may encounter an error code on the front panel as well as strange high pitch noises on higher gain settings and some buttons may not function properly. To restore the amp to normal operation you must change out the battery and perform a factory reset. The reset procedure may have to be done more than once. To reset the unit, hold OD1 and Clean 1 while powering the unit on. If you saved your settings through a MIDI dump they can be uploaded back to the unit after the reset has been performed.

Below is link to the full schematic and handbook. Programming these can be a little tough so it's good to have the handbook available. These units work great when paired with a proper MIDI controller like the Behringer FCB1010.

https://drive.google.com/drive/folder...