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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.

Marshall JMP-1 Factory Reset

  1. Switch off JMP-1 via the power button on the far right.
  2. Hold down the <OD 1> button and the <Clean 1> button.
  3. While holding down these buttons, switch on the JMP-1.
  4. Wait a few seconds while the display flashes and then release the OD 1 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 until you unprotect your JMP-1's memory.

To check the memory protect 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 it prior to performing a factory reset.

Unlocking is simple. Just follow this procedure:

  1. Try to save a patch.
  2. While 'St L' is displayed, press the <CHANNEL> button.
  3. The unit will unlock.
  4. You can now perform a factory reset as above.


While you're here, you may find it useful to know how to dump the entire memory of your JMP-1 to a sequencer or sysex package like MIDI-Ox or SEND-SX.

  1. Just connect the MIDI OUT from your JMP-1 to the MIDI IN of your sequencer or computer's MIDI interface.
  2. If using a computer, select that port in your sysex package.
  3. Now just press <Patch> and <Volume> simultaneously on your JMP-1.
  4. THE END!

IĀ  hope this Marshall JMP-1 factory reset procedure helps a few people but if you get seriously stuck, just message me. šŸ™‚

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:

Marshall JMP-1 Service
Marshall JMP-1 Needs Attention
Eclipse Marshall JMP-1 Data Encoder Fix
Marshall JMP-1 Nuts, Knobs and Bezels

Marshall JMP-1 Knobs Nuts and Bezels

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!!!! šŸ˜€ 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.

And here it is... my PML TX-01 transformer for the Marshall JMP-1
And here it is... my PML TX-01 transformer for the Marshall JMP-1