29 Oct
2024
29 Oct
'24
6:54 p.m.
2) motor speed
is not as easy as increasing/decreasing voltage.
On a belt driven drive, you might be able to change pulleys. Althoug, I
think that a "50Hz" pulley on a "60Hz" drive might give you the
change
from 300 RPM to 360RPM?, . . .
Some/many?/all? 8 inch drives use synchronous motors (8 inch drive power
connections were NOT standardized!) with one of their voltages being a
lowered voltage AC
I've never seen a 5.25" or smaller floppy
drive with a mains
sychronous motor.
Nor I. I don't recall ever seeing a 5.25", 3",
3.25", nor 3.5" that used
anything other than 5VDC and/or 12VDC
Almost all of the 5.25" (and, I think 3") used the same "molex"
connector.
I have a 3.25" drive that uses the same connector as 3.5", BUT different
postions for the voltages!
As an aside, Tektronix used normal 8" drives in
some of their
machines, always fitted with 60Hz pulley sets. They produced a 115V
60Hz output in the power supply, frequency contolled by a crystal. As
a result said machine would run off 50Hz mains, 60Hz and indeed 400Hz
aircraft supplies without pulley changes
How much 115VAC power do they produce?
3) 360K and
1.2M require different current level for writing. 1.2M drives
will generally have a signal (pin6?) for choosing current
It was pin 2 on the
original PC/AT 1.2M drive (I've just checked the
TechRef) and I would guess most clones did the same thing. The other for the PortablePC and PCr. Black panel, no
asterisk. A Qumetrak 142.
I've got a PortablePC (5155) in bits on the bench at the moment. I
don't much like those Qumetrak drives to work on. I have the IBM
TechRef and the Qume service manual. Both contain schematics. The
schematics do not agree with each other, or with either of the drives
in my machine (which are both IBM labelled Qumetraks and are slightly
different....)
Quite why IBM used 2 different drives from different manufacturers I don't know.
Because one couldn't supply drives with an asterisk?
or because they didn't want to use the crappy Qume 142 drives on anything
else?
The Qume 142 was so slow stepping, that that was one of the reasons for
introducing PC-DOS 2.10, to have a slower step time.
--
Grumpy Ol' Fred cisin(a)xenosoft.com