This document explains how to modify some PC floppy drives to output a RDY-Singal. This signal is required by the CPC for best compatibility.
Mitsumi D359T3
There is a small SMD resistor on the back of the circuit board marked with the number [b]D.C.[/b]. Next to it is an empty solder pad marked with [b]RDY[/b]. Desolder the resistor and move it to the RDY-Position. The drive now outpus a RDY-Signal. Additional information and pictures at [1] (german, but at least the picture is helpful)