27 Jan
2014
27 Jan
'14
10:26 p.m.
> There was one that was only good for testing the
speed of the drive,
> you could adjust with a screwdriver. But that's all it did.
For SOME drives, that's what needs adjustment most.
I remember having frequently having to deal with alignment on Shugart
5.25" drives, but rarely having to do anything with the MPIs other than
setting motor speed.
On Mon, 27 Jan 2014, Tony Duell wrote:
A lot of drives (I forget if the 1541 is one fo them)
have a stroboscopic
disk on the spindle. You adjust the motor speed so tht this appears
stationy under mains lighting (there are nomally 50Hz and 60Hz patterns
on the strobe). Some yeats ago I built a device with a few counter ICs as
a divider chain to flash some white LEDs at eitehr 100Hz or 120Hz
(rememebr a mains lamp flashes twice per cycle). I designed it so said
LEds were on 1/16th of the time. The result gave the clearest indication
of when a drive was on-speed that I have ever seen.
Long ago, a friend took one of my old automotive timing lights and rigged
it up to trigger off of the mains voltage.
But, I've been pretty happy with software speed testing (on drives that
have an index signal), and managed just fine with that for speed
adjustment.
[Drives dying]
But, there are other parts, including head assemblies that are not so easy
to work around.
Or how long before the caps on the boards go?
This is not a major problem. Capacitors are still made. And it's not a small machine. There's
112Mbytes of RAM in there. Programs
are large. Forget tryign to understnad them all.
It's pretty small. I think that a LOT of them would fit on a bus. :-)