Thanks for sorting out the Rainbow driver
Sorry, i dont have deep links on Bitsavers for you.
(see circuit at bottom of screenshot)https://dl.dropboxusercontent.com/u/37819653/BANNISTER/HLD%20-%20HLT%20-%20MOTOR%20ON.jpg
Source: Field Maintenance Print Set / MP-01722-01 from 1984 where the schematics of the RX50 controller can be found (scroll to end of document). https://archive.org/details/bitsavers_decrainbowwSchematicJul84_3508632
Page 231 of the OCR version of Rainbow Technical Manual (pc100tm1_text) explains how the Head Load Circuit works -
- Disk present in the selected drive and the door is closed (DISK P H)
- drive is selected and the spindle motor is turned on (MPWR SEL H)
From the RX-50 Dual _Diskette Drive_ Specs:
Head settling time: 30 ms (maximum value)
Head load time: 30 ms (maximum value)
Source : QV069-GZ 100+ 100B Technical Documentation Apr85
That's about it all i could find.