On Mon, Oct 28, 2024 at 6:45 PM Fred Cisin via cctalk <cctalk@classiccmp.org> wrote:
> 2) motor speed is not as easy as increasing/decreasing voltage. > On a belt driven drive, you might be able to change pulleys. Althoug, I > think that a "50Hz" pulley on a "60Hz" drive might give you the change > from 300 RPM to 360RPM?, . . . > Some/many?/all? 8 inch drives use synchronous motors (8 inch drive power > connections were NOT standardized!) with one of their voltages being a > lowered voltage AC I've never seen a 5.25" or smaller floppy drive with a mains sychronous motor. _Most_ 8" drives, including all the ones I've worked on, did use such motors but I've read an 8" drive service manual where the spindle motor was an electronically-controlled DC motor running off the 24V supply. As an aside, Tektronix used normal 8" drives in some of their machines, always fitted with 60Hz pulley sets. They produced a 115V 60Hz output in the power supply, frequency contolled by a crystal. As a result said machine would run off 50Hz mains, 60Hz and indeed 400Hz aircraft supplies without pulley changes > 3) 360K and 1.2M require different current level for writing. 1.2M drives > will generally have a signal (pin6?) for choosing current It was pin 2 on the original PC/AT 1.2M drive (I've just checked the TechRef) and I would guess most clones did the same thing. > So, that will require a work-around. > (also, READY/DISK CHANGED signal was not completely standardized.) > > > AFTER coming out with the 1.2M drives, it bagan to be important to tell > them apart. So, getting it backwards?, they started embossing an asterisk > on 360K drives. So, any drive with an asterisk is 360K, a drive WITHOUT > an asterisk might be a 1.2M, OR might be a 360K from before they added > asterisks. It's worse than that! IBM had 2 half-height 360K drives. One for the PC/AT with a light grey panel. It has the asterisk. Made by YE Data I think The other for the PortablePC and PCr. Black panel, no asterisk. A Qumetrak 142. I've got a PortablePC (5155) in bits on the bench at the moment. I don't much like those Qumetrak drives to work on. I have the IBM TechRef and the Qume service manual. Both contain schematics. The schematics do not agree with each other, or with either of the drives in my machine (which are both IBM labelled Qumetraks and are slightly different....) Quite why IBM used 2 different drives from different manufacturers I don't know. -tony
