Another replacement encoder found!
I can confirm that this encoder by ALPS also works:https://ie.rs-online.com/web/p/mechanic
USA link: https://americas.rsdelivers.com/product ... al/2651739
Not stocked at Mouser or Digikey
ALPS Part number: EC16B242040R
Please excuse my horrible soldering job, my eyesight has gone bad for close-up work and the space was very tight with the length of cable available. Joints are fine and if it stops working I'll go back and tidy up.
As you can see, there's a nipple on the new encoder that fits perfectly into the mount for the old encoder.
I can't be sure my old encoder had not been rewired, so I'm not going to say "old pin 1 to new pin 1 etc".
Wiring is as follows, L to R from above,
1. VVVVVVVVV marked wire
2. Blue striped wire
3. Manufacturer's name wire
The shaft is d-shaped, unfortunately.
I just happened to have a spare D shaft knob with a skirt that had the exact diameter of the original aluminium MPC60 encoder knob, so I removed the plastic insert, cut the height of the D shaft knob to fit and glued it into the original using Evo Impact adhesive. The knob is a Buchla 200 series knob, readily available online should you wish to do the same.
Sorry for instagram link, doesn't seem to be a way to upload directly here.