Experience with Dysan drive tester?

Tony Duell ard at p850ug1.demon.co.uk
Wed Oct 3 16:59:20 CDT 2007

> A friend might have a Dysan Pat-2+ 5.25" floppy drive tester held for 
> me, but we both have no experience with it.  Assuming it comes with the 
> alignment disk and manual, and functions, is it a worthwhile piece of 
> equipment to have?  I am not a die-hard techie -- I do not own an 
> oscilloscope -- so I might grab it to keep my drives aligned, but not if 
> it's more placebo than functional.
> If anyone has had experience using this unit or one like it, I'd like to 
> hear your thoughts.

I don't know this particular unit, but this sounds like a 'drive 
exerciser', and I have one of those. 

A drive exerciser basically simulates the host interface to a floppy 
drive. It lets you select the drive, load the heads, step the heads in 
and out (good ones lwt you go to particualr tracks directly, move the 
heads and forth automatially, etc). It'll monitor the write protect, 
inde, track 0, etc lines and display them on front panel LEDs. Most of 
them also let you write a continuous square wave at a couple of selected 
frequencies to the currently selected track.

But you do need a 'scope to use one. FIrstly to look at the waveform read 
back form the disk (e,g, after writing one of those test frequencies), 
and secondly to do the alignment. Typically to do the 'radial alignment' 
(gettign the head on the centre of the track, what most people mean by 
'alignment' here), you put the alignment disk in, move the heads to the 
CE track using the exerciser, then monitor the outputs of the read 
amplifier in the drive (2 testpoint on the drive PCB) with a 'scope and 
move the stepper motor or whatever until the 2 loes of the CE pattern are 
the same szie.

If you don't have a 'scope, there was a thing sold in the UK (designed 
over here too I think) called a 'Microtest'. You used that with a PC (the 
minimum spec, was I believe, 256K RAM, 1 serial port, 8088, any video 
card, even MDA). You linked up the drive-under-test as drive B to the PC 
(there were cables included with the Microtest unit for this), connected 
the Microtest box to the serial port (this was a box containing a 
microcontroller, ADC chip, etc, and which drew poer from the RS232 port) 
and ran the Micortest software on the PCB. You then selected the drive 
type from a menu of about 300 types, and it displayed a picture of the 
drive PCB on the screen (using the IBM block graphics characters) and 
told you where to connect 5 leads coming from the Microtest box.

You then put a stnadard alignment disk in the drive. If, say, you wanted 
to do the radial alignment, you presss the approrpiate function key, the 
ehads moved to the right track, and the mcirotest unit effectively 
measured the amplitude of the 2 CE lobes. The result was displayed on the 
PC (again using IBM graphics chracters) as was the distance that the head 
was from the right position, and whether it was in tolerance. You moved 
the head stepper until it was where it should be.

What do I use? Both :-). The Microtest (I was given one) is useful for 
quick test and alignments on basically working drives. The exerciser is 
useful to figuring out why the heads won'y move in the first place, or 
why the write cirucit is blowing transistors, or...


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