Ten Year Rule

Fred Cisin cisin at xenosoft.com
Thu Nov 26 13:39:22 CST 2009

> > I have been told that that calls for dual-trace and 20MHz or higher.  Is
> > that correct?

On Thu, 26 Nov 2009, Tony Duell wrote:
> Only because that's about the loswst spec you'll find in a modern 'scope.
> >
> > Eventually, I gave it to somebody who needed it more than I did, and I got
> > myself a used NLS 215.  Still not enough for floppy drive alignment.  But
> Did you actually try to align a floppy drive with it?

I did try a number of times, but my lack of expertise (TOTAL IGNORANCE of
what I was doing) got in the way, and I trusted the advice of "experts".

But, it was still very useful and fun.  I used both scopes for automotive
diagnosis.  For example, it isn't very easy to find out that the problem
with an alternator ("just replace the whole thing!") was a diode (three
phase rectification) without a scope.

> Actually, if you want to align floppy drives (and nothing else), I would
> try to find a thing called a 'Microtest'. It's a box containing an ADC
> and a microcontorller that links to a PC serial port (_Any_ PC with a
> floppy controller and a serial port, I think you need 256k RAM and any
> display adapter, even MDA). You link up the drive under test as drive B
> on the PC, and run the software that comes with the microtest. Then
> select the drive from the menu (and there's every one that _I've_ ever
> wanted to work on), it drwas a picture of the drive PCB (using IBM
> line-drawing characters) and tells you where to conenct 5 clip-leads from
> the ADC box. Then put in a standard analogue alingment disk and it will
> tell you how far off-track you are, if the track 0 sensor is correctly
> positioned, and so on.

That sounds sweet, and likely out of my price range.

I liked using the Dysan Digital Diagnostic Disk, and wrote some code for
additional unsupported machines, but I could never shake the feeling that
I wasn't able to do as good a job as an analog alignment.

> > Can you imagine what the world would be like if NLS had gotten into making
> > computers?  :-)   They'd probably grow faster than they could manage, and
> I assume that is very much tongue-in-cheek...

Completely.  I even stuck an emoticon in there in case anybody didn't get

In college, I wanted to learn electronics, to design a few toys with
integrated circuits, and understand the computer internals, but was always
busy with other stuff, and the college required multiple semesters of TUBE
electronics before getting to transistors, and only got to ICs in the
final "advanced topics" course.

What an idiot I was.  NOW where can I find a fun course for playing with
tubes ("valves"?)

Grumpy Ol' Fred     		cisin at xenosoft.com

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