28 Oct
2024
28 Oct
'24
6:37 p.m.
On Mon, 28 Oct 2024, Fred Cisin via cctalk wrote:
Converting drive: (NOT PEACTICAL!)
1) Disk controllers intended for 360K generally run 250K bits per second
(125K for single density), and do NOT support the 300K bps and 500K bps
that are needed.
Weltec sold some drives with a VERY bizarre work-around, by making the
drive of a 1.2M drive spin at 180 RPM! 180 RPM with 250kbps being
equivalent to 360RPM at 500K bps
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
BTW, NEC APC? ran their 3.5" 1.4M drives at 360RPM, instead of 300RPM.
That meant that all three of their sizes (8", 1.2M 5.25", 3.5") could have
the same format!
Some Japanese 3.5" drives (called "3 mode?") canswitch between 300 and
360RPM!
3) 360K and 1.2M require different current level for writing. 1.2M drives
will generally have a signal (pin6?) for choosing current
So, that will require a work-around.
(also, READY/DISK CHANGED signal was not completely standardized.)
AFTER coming out with the 1.2M drives, it bagan to be important to tell
them apart. So, getting it backwards?, they started embossing an asterisk
on 360K drives. So, any drive with an asterisk is 360K, a drive WITHOUT
an asterisk might be a 1.2M, OR might be a 360K from before they added
asterisks.
If you convert any drives, be sure to add or remove asterisk :-)
A label maker would help with that, and also lable which drive is
"A" or "B"
--
Grumpy Ol' Fred cisin(a)xenosoft.com