So in case your Marshall JMP-1's memory gets screwed up, if you just want to start from a clean slate or you've just changed the memory back-up battery, here's the Marshall JMP-1 factory reset procedure.
WARNING: Implementing this procedure will permanently delete all user-made changes to any patches.
- Switch off JMP-1 via the power button on the far right.
- Hold down the OD1 button and the CLEAN 1 button.
- While holding down these buttons, switch on the JMP-1.
- Wait a few seconds while the display flashes and then release the OD1 and CLEAN 1 buttons.
Now then, you're JMP-1 might NOT reset! Yes, that's right. If your machine is locked, performing a factory reset will be useless unless you unlock your JMP-1 first.
To check the 'SAVE' status of your JMP-1, simply try to save a patch. If the display shows 'St L', then your JMP-1 is locked and you will need to unlock prior to performing a factory reset.
Unlocking is simple. Just follow this procedure:
- Try to save a patch.
- While 'St L' is displayed, press the <CHANNEL> button.
- The unit will unlock and the display will show the current channel to save to ex: "St 01".
- You can now perform a factory reset as above.
I hope this Marshall JMP-1 factory reset procedure helps a few people but if you get seriously stuck, just message me. 🙂
If you want to read more about what I do with JMP-1s, like general service and repair, finding a permanent solution for the skipping data entry knob thing, sorting out the humming transformer issue and offering nice, classy replacement knobs, then please check out some of my other posts:
Apart from service and repair, I sell a few bits 'n' pieces for the Marshall JMP-1 which you may find of interest. Check out my on-line store to find out more.
UPDATE - 21st September 2021
At last!!!! 😀 My PML-TX01 replacement (and upgraded) transformer for the Marshall JMP-1 is finally here! Running much cooler and producing considerably less hum than the original TXMA-00014 my PML-TX01 is an upgrade worth considering.