Testing floppy drives

tony duell ard at p850ug1.demon.co.uk
Thu May 28 12:43:29 CDT 2015

>     Since it is not pratical to test all these drives on CP500, is there a
> good software solution I can use on a PC for floppy drive testing? Something
> that makes repairing easier? Long time I don't get so many drives to
> repair/refurbish/align

IMHO the ultimate PC drive exerciser was something called a microtest. This is a 
combination of hardware and software. The hardware is an 8035 microcontroller 
+ ADC that was connected (and powered by) the PC serial port. The drive under
test was connected to the PC as B: and the (alas closed, proprietary) software run
(it would run on any PC compatible, IIRC the requirements were something like 
256K RAM, 1 serial port, any video card, even MDA). You then selected the drive
from a menu of many hundreds of drives. It displayed a diagram of the drive
PCB and you connected half a dozen grabber clips from the ADC box to the right
points on the PCB. It would then let you do all the drive alignments using the normal
catseye disk but without needing a 'scope.

I have no idea where you'd find one now ('On top of the small bookcase in my
bedroom, under the Heathkit aircraft navigation computer' is true, but not
much help). But it is something to look out for. I modified an old Amstrad PPC 
laptop to have a DC37 socket in the B: drive bay so I could hook up an external
drive under test and use the Microtest with it.

A dedicated drive exerciser that lets you do repeated seeks, etc, is useful too. In general
you _don't_ need to handle the read/write side at this stage, just checking the status
lines, sending step and direction signals, and if possible checking the frequency of the index
pulse. Years ago I used the parallel port on a PC for this (to work with a strange drive that my
normal commercial stand-alone exerciser couldn't handle), it seems to me this is the sort of 
thing you could trivially do with a microcontroller that has enough I/O lines.


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