Steve,
If you could get a measurement of the diameter of the inner aluminum core of the VOLTS/DIV knob I can try making a casting from one of the knobs on my 485. If that goes even passably well I can send you the resulting plastic shell which you could use to mend your shattered plastic. I expect that the casting will not fit flush against the metal core, but that can be remedied with some needle files and manual effort.
I have done something similar to repair the VOLTS/DIV knobs on a 475A, but I used the remains of another knob. I've been working on my casting techniques because I would like to be able to repair such broken knobs without reducing the overall supply.
-- Jeff Dutky
