24 Apr
2011
24 Apr
'11
7 a.m.
On 4/24/11 7:56 AM, Shoppa, Tim wrote:
Eric writes:
I always had very good luck with ST-225s. I ran one or two at home,
and installed lots of them in customer machines.
One important thing for ST-225s and ST-251s is to not tighten the
screws at all four corners. After many unexplained high-error-rate
installations, we determined that the drive's metal substrate twists
slightly due to thermal expansion when the drive heats up, throwing off
the head/track alignment. These drives don't use any sort of
servo-positioning scheme to maintain head/track alignment; they use a
stepper motor arrangement similar to that of many floppy drives, so any
mechanical drifting doesn't get corrected. Leaving two
diagonally-opposed screws loose solved the problem in every case.
-Dave
--
Dave McGuire
Port Charlotte, FL
Fred Cisin wrote:
Most of my suffering with MFM drives happened at the upper end of
the cost/complexity spectrum.
Looking back 20 years I in fact have good respect for the simpler of
the MFM drives and the ST-225 is an example.
Maybe my expectations were just lower for a drive that didn't cost
$4000 (list price of a XT-2190). But it's also quite true that ST-225's
didn't crap out at the rate as the much more expensive MFM drives
and for that I have to really give them some credit. "trusty ST-225"??
Well, as
compared to some brands, yes. JTS comes to mind, though it
wasn't contemporary with the ST-225.