Quote:
Won't the old knob work with some "electrical tape" molding to fill in the gaps?

Probably not very well. The old knob relied on friction, and if the shaft isn't round then some of the friction is gone. You can't glue the knob because then you'd never get the faceplate off again.

Much better to either (a) replace with a Mk2 encoder, or (b) get a 2a knob from support as part of the transaction.
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Tony Fabris