3.25-inch floppies

[Tony Duell]

> > > Only as far as type and utility goes.  A modern 3.5" drive is just as 
> > > useful as an old Sony 0AD SS 3.5" drive, even if it only spins at 300 
> > 
> > Not if you're restoring an HP drive unit, or an Apricot, or... it isn't!
> 
> I wonder if a DSHD 3.5" drive could simply be persuaded to spin the 
> diskette twice as fast--they certainly run just fine at 360 RPM.  
> I've never had to address the 2X issue (I'm more interested in 
> reading disks from the old gear than restoring the old gear).  
> 
> Some of the old duplicator equipment used 2X and 4X drives, so 
> there's another source for you.
> 
> Or the FDC clock rate could be halved and a normal drive be used.

Oh quite likely any of those things _could_ be done, and may have to be 
done sometime, but for now I'd ratehr keep the machines are original as 
possible and repair the existing drives. I am not one of these collectors 
who insists on every part having the right date code, but I don;t like 
changing the design _at all_. 

Most of tyhe time the problem is hardened grease on the eject mechanuism, 
which is easy to cure by taking the thing apart and cleaning up the 
parts. The problem comes if it's not been caught in time, but instead the 
upper (down) head has been caught in the disk shutter when the disk is 
ejected. Then it's time for a new head assembly, which you have to raid 
from a similar drive. Single-head drives suffer from hardened grease just 
the same, but of course the head doesn't get damaged

I've not had a fault on the main logic board yet. There is a 
mask-programmed microcontroller (not supriningly), but everything else is 
standard. I have had problems with the spindle motors in the doule-head 
models. One time the motor commutator chip died, it's a standard one used 
in VCRs, etc, so I could find a replacement. Another time a hall sensor 
failed, I raided one from the motor in a drive where I'd already taken 
the head carriage.

I ahve never had to do a head alignemnt. I've replaced head assemblies. 
put the alignment disk it and found the CE patten to be well withing 
tolerance. According to the docs I have there were at least 3 special 
tools used for a full analignemt, one was a knob to fit on the stepper 
motor spindle and allowthe latter to be tuned by hand (easy to make). One 
was a tool like a screwdrier but with a pinion at the business end, used 
to turn the stepper motor. That's probably makable too, but I'd love to 
see an original one and count the teeth, etc. The last was a weight used 
to check the head compliance, I would love to borrow one of those and 
measure the mass.

-tony