[cctalk] Re: Floppy disk

The original 23FD drive as used in the 3830 control unit for 3330 DASD was a read only device and I remember one of the large system CEs showing me the diskettes for them, the sleeve was much stiffer than later diskettes. The read/write 33FD was first shipped in 1973 and when I started at IBM in 1979 several of the terminal controllers started up from one of them.  The head carriage was moved by a crude stepper that turned 90 degrees per step and was coupled to the bottom of a lead screw by a Geneva drive.  The drives did not have a track zero sensor so when initialize they would take about 80 down steps. There where collars fixed on the lead screw that limited the travel and the one at the bottom would hit a plastic tip on the head carriage to stop the head at track zero, and when being initialized would hammer on the down stop several times especially if the head was already close to track zero.  In my early days as a CE I was thrown into fixing a S/34 that I knew nothing about but it turned out to be a problem with the 33FD diskette drive that I was familiar with from working on terminal controllers, the down stop had broken off the head carriage.  I was at a remote location and had no parts, but was able to fix the S/34 by swapping its drive with one from a 3742 the customer was returning to IBM. Before I left field service the first time in 1983 double sided drives where already starting to appear, these drives had a proper stepper motor and a taught band to move the head carriage, but still did not have a track zero sensor. Several years later I was a hardware support person in the Toronto Lab and one of the rooms I looked after had a 3880 controller with a couple 3380 DASD units and the first time I heard the 3880 start up I thought I know that sound, so I looked inside and sure enough it IMLed from a 33FD. Paul. On 2026-06-08 22:46, William Donzelli via cctalk wrote: