CompuPro floppy controller differences

[Tony Duell]

> Hi
> A friend has an older Celestron telescope with an AC clock drive.
> We took one of those 12v to AC converters and added a couple pots
> and switches to vary the frequency for tracking the telescope while
> doing photo work. The converter used simple 555 circuits to control
> the frequency so it was relatively easy to modify.

As a somewhat-related aside, IIRC there's a circuit in at least one 
edition of tAoE to produce a not-quite-60Hz sine wave at 115V. Used to 
drive a synchronous clock motor and get it to display sideral (rather 
than mean solar) time.

-tony