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Screw Kit for the Marshall JMP-1

In response to a question I get asked a lot, "where can I get screws for my JMP-1?", I've decided to release a complete screw kit for the Marshall JMP-1.

Screw kit for the Marshall JMP-1

Yeah, I know... it's not a big deal but it's just one of those things in life that niggles us, especially if you have a JMP-1 with err... missing screws!

The JMP-1 was produced with some interesting hardware:

  • All the screws are black... err, except for one of the big earthing screws that secures to the chassis. The other earthing screw is err... black!
  • Some screws are Phillips cross-head and some are hex-head… oh and at least two are flat-head (seriously?).
  • Most are M3.
  • Most are machine screws but three are self-tap.

Surely it would have been cheaper for Marshall to at least use all the same type of screws but hey, it was Bletchley, 1992.

Marshall JMP-1 screws
Perhaps Marshall ran a competition for the staff: "How many different types of screws can we get into the JMP-1, guys?"

Another conundrum is why did Marshall use ordinary washers and spring washers on the earthing points, when they used nylon locking nuts. They didn't do that with the locking nuts that secure the IEC C14 power connector. My screw kit for the Marshall JMP-1 omits those superfluous spring washers and since the holes in the rear chassis for the IEC C9 aren't threaded, my kit replaces the weird flat-head screws here, with standard metric cross-head types.

Another tweak in my screw kit, is that the three screws that secure the top-case (lid) to the bottom-case at the rear of the unit, look quite different. The screws in this kit replace the original wide-head screws that Marshall used, with more elegant, standard-headed screws. They fit perfectly and are considerably less obtrusive.

More elegant rear screws for Marshall JMP-1
Perhaps slightly more elegant standard-headed rear screws for Marshall JMP-1.

With only cross-head screws in my screw kit for the Marshall JMP-1, you only need one screwdriver! 🙂 Yeah, okay... two then (a medium cross head and a smaller cross head).

I would have liked to keep everything the same but unfortunately, those three screws at the rear of the unit, that secure the lid to the bottom-case as mentioned earlier, have to be self-tapping.

There's no manual supplied supplied with this kit but there is a pretty comprehensive hardware guide that's available after purchase, just to make sure that you put the right screws in the right places. 🙂

Here's a list of the contents of my screw kit for the Marshall JMP-1 (total number of items = 29)

  • 3 screws for rack-ear left
  • 3 screws for rack-ear right
  • 2 screws for IEC C14 power inlet connector
  • 2 screws for internal front panel PCB bracket
  • 2 locknuts for IEC C14 power inlet connector
  • 3 screws for rear chassis
  • 2 screws for front facia top
  • 3 screws for front facia bottom
  • 1 screw for top-case front
  • 1 screw for earthing point left side of case
  • 1 screw for earthing point in front of transformer (bottom case right)
  • 1 washer for earthing point left side of case
  • 1 washer for earthing point in front of transformer (bottom case right)
  • 1 lock nut for earthing point left side of case
  • 1 locknut for earthing point in front of transformer (bottom case right)
  • 2 screws for footswitch port on rear

A complete set of screws for the Marshall JMP-1

One thing I really must emphasise is that unless your Marshall JMP-1 is going on a deep-space mission, please (PLEASE) don't over-tighten the screws!!!!

If you do over-tighten, you might end up threading a screw hole or two and if you ever have to open up your JMP-1, having to undo tightened screws, increases the risk of screwdriver slippage and hence, damaging something. You could also mess up the odd screwhead and if that happens, you might have to drill out a screw and that's not good.

Something else I get asked a lot for, are the rack-ear reinforcement brackets and so I decided to have a go at designing some replacements. In fact, at the time of writing, I'm waiting for some protypes to be made by my friends at Lenton Engineering. I'll keep you all posted about them.

And in case you've missed some of my stuff, here's a bunch of other bits 'n' pieces that I make for the Marshall JMP-1:

Fix the skipping encoder

Spare knobs, bezels and power button kit

PML-TX01 replacement transformer for the Marshall JMP-1

CR2032 battery adapter for the Marshall JMP1

RE-JMP-1 replacement rack-ears for the Marshall JMP-1


Check out all of my Marshall JMP-1 stuff in my on-line store...

Marshall JMP-1 stuff at Plasma Music