28 Nov
2010
28 Nov
'10
5:37 a.m.
Hi guys,
As you might have gathered from my other thread, I'm toying with the
idea of building a replacement controller card for my two dead
double-sided Amstrad disc drives. Ideally I'd like to use as many
"standard" parts as possible to ease debugging and future repair. I'll
probably use a GAL to handle head-stepping and the write protect
lockout, and LSTTL for the bus interface.
Hmmm.. I am not sure that easing future repair and GALs (or any other PLD) go
together. Well, not unless you etch the logic equations into the PCB :-)
I've got my hands on a couple of Texas Instruments
MC3470A floppy disc
read amplifier ICs, and the Apple Disk II schematics suggest how this
can be tied to a drive mechanism. What I'd like to do is look at a few
other drives which use this chip to make sure I understand everything
correctly (a double-sided drive with a single 3470A would be handy). If
I'm being honest, the TI datasheet for the chip is utter crap...
'My' schematics for the HP9826/36 (available from http://www.hpmuseum.org/)
include schematics of the MPI drive, which is a double-sided 5.25" unit using
the 3470. There are also schematics of a Tandon-based drive using a read
amplifier based on the uA733 and NE592 amplifiers (another common circuit -- it
works well, but do take care with the layout!).
-tony