18 Mar
2014
18 Mar
'14
1:14 p.m.
----- Original Message -----
Date: Tue, 18 Mar 2014 07:14:36 -0400 (EDT)
From: Steven Hirsch <snhirsch at gmail.com>
On Mon, 17 Mar 2014, MikeS wrote:
----- Reply: -----
Then maybe the step rate is just too fast for those drives? Some systems did
have an option to set the step rate depending on the drive type.
Are the rails immaculately clean, i.e. no unusual friction? Maybe try
exercising one of the drives for a bit to see if that helps...
Any chance it has a jumper setting that puts it
into double-step mode and
emulates a 'normal' 40 track drive (albeit with a narrow head)? AFAIK RPM
and
current would be the same.
Could be, but that doesn't explain why it seems to single-step when a
train of pulses arrive at the max rate, yet double-step when they arrive
individually.
I really hate to write off these two drives. They are incredibly clean
units, probably NOS and were top of the line in their day.
Steve 
18 Mar
18 Mar
2:16 p.m.
On 03/18/2014 10:14 AM, MikeS wrote:
Then maybe the step rate is just too fast for those
drives? Some systems
did
have an option to set the step rate depending on the drive type.
Are the rails immaculately clean, i.e. no unusual friction? Maybe try
exercising one of the drives for a bit to see if that helps...
Alos, try cranking the step rate down to 15 msec. or so. It seems that
the FD50A is a very slow drive:
https://groups.google.com/forum/#!msg/comp.sys.tandy/RsbfOaWXxog/bJykbvKE5s…
--Chuck
2:47 p.m.
Are these the Teac plastic-frame belt-driven drives?
If so, they were far from top-of-the-line models.
Right now, I'm trying to figure out the model labeling. The 50A seems
to be a 35 track, single-sided.
--Chuck
6:25 p.m.
On Tue, 18 Mar 2014, Chuck Guzis wrote:
Are these the Teac plastic-frame belt-driven drives?
If so, they were far from top-of-the-line models.
Right now, I'm trying to figure out the model labeling. The 50A seems to be
a 35 track, single-sided.
Ugh. I was misreading the table of features in the tech docs... I
thought the rows were keyed on the numeric suffix of the _drive_ model,
but I think it was really talking about the PCB revision. Now that I look
again, the drive models appear to be:
FD-50A 48 TPI
FD-50C,D,E,F 96/100 TPI (??)
So this is indeed a 35-track drive with deathly slow step rate. I will go
back and re-test with this in mind.
Thanks for keeping me honest!
Steve
--
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