Epson SMD-400 drive - test-drb@ccmp.vtda.org

18 Apr 2011

If so, it's the first one I've heard of in a floppy drive, but anyway...

...
   >  It is
indeed a rack-and-pinion positioner.  That is unusual. I think it would be worth
trying to restore this drive,
 if only to have a working example of such a mechanism
 Good point. I don't think they are terribly rare, they probably turn up 
on eBay every so often, and Atari 1040s aren't rare. OTOH they seem to 
have used a variety of drives.
I shall see what I can do to get it working again.
...
  > >  >
 You would want som way to eliminate the backlash between the rack and the
> >  >  drive gear. One common way to do thsi is to make the gear in 2
'slices'.
> >  >  One is fixed to the spidnle, the other is free to move by a small angle,
> >  >  but there;s a bias spring forcing it in a particualr direciton relative
> >  >  to the spindle. The idea is that said spring is pre-tensioned when the
> >  >  mechnaism is assembled so that the teeth of the 2 gears are forces to
> >  >  commpletel fill the gaps between the teeth on the rack.
 >  I know what you mean. There is nothing like that here, everything is
 >  probably too small. The pinion is about 2 mm diameter and the teeth on
 >  the rack are something like 3 per mm...  3 teeth per mm? That's a very
fine pitch.

 Thinking about it, 3.5" 80 cylinder drives have 135 tpi. So the track
 spacing is 1/135" or 0.19mm. The backlashj in the mechansim must be a lot
 less than that, I guess with a 0.3mm pitch rack you can get that.
 3 per mm was a guess, but I can't see the teeth on the rack with my 
naked eye (i.e. wearing reading glasses only). I need a magnitying glass 
to see that there are teeth at all.
...
  > >  >
 What I would do next is with the drive removed, try carefully moving the
> >  >  head back and forth and/or rotatign the stepper motor spindle and see
> >  >  what moves. If something is stripped then moving the head will not
> >  >  rotrate the motore and vice versa. Of course you may find that something
> >  >  is jammed solid, in which cae that could be the problem.
 >  I removed the motor, it turns out the rack and the pinion is in good  As soon
as you remvoed tht motor, you lost the head alighment... Any alignment must be
totally lost by now. But if I do get it working I 
can format a disk on it and see if that works. Reading and writing files 
might be more of a problem, I can't remember if there is any way to 
create directories and files in the bare OS, or if one needs programs 
...
 from another disk, in which case I would be out of luck
if it is so  badly misaligned that it can't read other disks.
...
   >  shape.
What I was seeing was just a deposit of grease and/or gunk. The
 >  head assembly was locked solid. It runs on a steel rod approx. 2 mm
 >  diameter which goes through what looks like bushes, and it was
 >  completely jammed from lack of lubrication, dirt etc. The bad news is
 >  that now everything is out of alignment since the head assembly came
 >  loose when I was trying to move it (it was locked really, really solid), 
Provide the head is not damaged, I'd try cleaning it up, making it work
 freely again, and then see if you can get the drive working. Even with
 the radial alignment way off, the drive should be able to read its own
 disks (ones formated in that drive).

 As for doing the full alignment, there are various ways of getting it
 somehat near using a disk formatted on a known-good drive, but it's a lot
 easier with an alignment disk and 'scope.
 If I get that far I shall have to try something. I have a 'scope but no 
alignment disk.
...
   >  and I
don't have an alignment disk. Still, it was a learning experience...
 >  I have ordered a new drive from a local shop, they don't keep them in
 >  stock. They are only 6 Euros so replacing it will be a lot less trouble 
Hmmm. I wonder if those cheap drives are ever aligned at the factory...
 I've seen new drives over here that are certainly marginal when checked
 against a good alignment disk.
 I shall soon find out :-)
...
   >  than
making it work again. I would have liked to fix it, but that is
 >  simply not practical, sadly.  I'm not convinced it's impossible.
 I didn't say "impossible" :-) I meant practical given my resources.
But 
then I may be underestimating myself. And I would of course have to be 
committed to taking the time to make it work. OTOH, why not?
...
   > 
Interestingly, Atari drives are sold for about $50 on eBay, with
 >  shipping to Sweden another $50. I suppose they are "collectable". That
 >  works out at about 10x the price of a new one. The difference is that
 >  the original drive is 720K and has a special bezel and eject knob, a new
 >  one is 1.44M and the bezel and knob can be transferred from the old one.
 >  The machine itself works with a 1.44M drive.  Hmmm... I guess I am more of a
purist, but I really don't like replacing
 modules (such as drives) in classic computers with random modern units.
 To me, the design of the drive is part of the design of the machine, and
 it should be preserved if at all possible.
 Indeed. It would also guarantee compatibility with all the old game 
disks I got with the machine :-) It is an interesting machine, I bought 
one ages ago instead of a PC. It was faster than the equivalent "turbo" 
PC, cheaper, the display was higher resolution and it also had very good 
built-in MIDI support. I used mine a lot, not only for playing games, 
but I also translated several books using it as a word processor, and 
ran accounting software on it. I think I even designed a PCB on it. 
There was a lot of good and really useful software for it, word 
processors, early desktop publishing software that was better than the 
PC software, CAD programs, and of course *lots* of music software. 
Musicians used it a lot, and I knew a chap who used his to drive a very 
big Roland plotter type machine that had knives instead of pens, to make 
signs by cutting sheets of plastic film. And GEM was way ahead of DOS 
and Windows at that time.

I could kick myself for getting rid of my first one... Well, at least I 
have one again :-)

/Jonas