Discussion:
How do I make a Shugart 390 drive do 40 tracks?
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retrogear
2017-08-26 19:27:56 UTC
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I have two MicroSci 5.25 drives which are Shugart 390 mechanisms. They look like identical drives except one will format out to 40 tracks but the other stops after 35. Was there a modification to make 40 track work? Seems like I remember that from 30 years ago but lost in the brain fog of time ...

Larry G
retrogear
2017-08-26 21:11:41 UTC
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Figured it out. The metal cam follower is different thicknesses between the two drives so a change in manufacturing. I suppose a dremel tool could be used but not doing that on mine. I think the metal pieces could be exchanged between drives.

Larry G
Mark D. Overholser
2017-08-28 23:37:03 UTC
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Post by retrogear
Figured it out. The metal cam follower is different thicknesses between the two drives so a change in manufacturing. I suppose a dremel tool could be used but not doing that on mine. I think the metal pieces could be exchanged between drives.
Larry G
That would mean that "new" Followers could be Machined and Older SA390's
could be Retrofitted...

I will need to pull out my Three SA-390s and check them.. I'll bet that
my Oldest One is limited to 35 Tracks....


MarkO
Mark D. Overholser
2017-08-29 14:22:07 UTC
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On Mon, Aug 28, 2017 at 6:37 PM, Mark D. Overholser
Post by Mark D. Overholser
Post by retrogear
Figured it out. The metal cam follower is different thicknesses
between the two drives so a change in manufacturing. I suppose a
dremel tool could be used but not doing that on mine. I think the
metal pieces could be exchanged between drives.
Larry G
That would mean that "new" Followers could be Machined and Older
SA390's could be Retrofitted...
I will need to pull out my Three SA-390s and check them.. I'll
bet that my Oldest One is limited to 35 Tracks....
MarkO
Let me know. If that follower is taken out, then the carriage
limiter adjustment needs to be done. I suppose photos could be taken
and markings made to put it back in >the same spot w/o having to do
the adjustment.
Larry G
Precise Marking and Before and After Pictures...


I have been very curious to know what, "The solution was to optimize the
analog electronics, tighten up the drive adjustment procedures and
build some test fixtures to make adjustments reasonable to do in
production." involved, according to this bit of Apple ][ History:
<http://www.apple1notes.com/old_apple/Huston_Stories_files/Disk%20SN1.htm>


MarkO
Anthony Ortiz
2017-08-29 19:08:30 UTC
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Post by Mark D. Overholser
On Mon, Aug 28, 2017 at 6:37 PM, Mark D. Overholser
Post by Mark D. Overholser
Post by retrogear
Figured it out. The metal cam follower is different thicknesses
between the two drives so a change in manufacturing. I suppose a
dremel tool could be used but not doing that on mine. I think the
metal pieces could be exchanged between drives.
Larry G
That would mean that "new" Followers could be Machined and Older
SA390's could be Retrofitted...
I will need to pull out my Three SA-390s and check them.. I'll
bet that my Oldest One is limited to 35 Tracks....
MarkO
Let me know. If that follower is taken out, then the carriage
limiter adjustment needs to be done. I suppose photos could be taken
and markings made to put it back in >the same spot w/o having to do
the adjustment.
Larry G
Precise Marking and Before and After Pictures...
I have been very curious to know what, "The solution was to optimize the
analog electronics, tighten up the drive adjustment procedures and
build some test fixtures to make adjustments reasonable to do in
<http://www.apple1notes.com/old_apple/Huston_Stories_files/Disk%20SN1.htm>
MarkO
That's one of my favorite bits of Apple II history; I think I read this in "Sophistication and Simplicity : The life and times of the Apple II computer"
Mark D. Overholser
2017-08-29 20:22:35 UTC
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Post by Anthony Ortiz
Post by Mark D. Overholser
On Mon, Aug 28, 2017 at 6:37 PM, Mark D. Overholser <mark>
<< SNIP >>
Post by Anthony Ortiz
Post by Mark D. Overholser
Precise Marking and Before and After Pictures...
I have been very curious to know what, "The solution was to
optimize the analog electronics, tighten up the drive adjustment
procedures and build some test fixtures to make adjustments
reasonable to do in production." involved, according to this bit of
<http://www.apple1notes.com/old_apple/Huston_Stories_files/Disk%20SN1.htm>
MarkO >
That's one of my favorite bits of Apple II history; I think I read
this in "Sophistication >and Simplicity : The life and times of the
Apple II computer"
I believe that <http://www.apple1notes.com/> is Wendel Sanders site....

MarkO
Mark D. Overholser
2017-08-30 03:14:17 UTC
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On Tue, Aug 29, 2017 at 9:22 AM, Mark D. Overholser
<< BIG SNIP >>
Precise Marking and Before and After Pictures...
I have been very curious to know what, "The solution was to optimize
the analog electronics, tighten up the drive adjustment procedures
and build some test fixtures to make adjustments reasonable to do in
<http://www.apple1notes.com/old_apple/Huston_Stories_files/Disk%20SN1.htm>
MarkO
I remember reading the story years ago how Shugart had given Apple
some of their "subpar" drives - funny.
Larry G
I wonder if Shugart
#1 ) Had "trouble" figure out what was wrong with them, or
#2 ) If they were just So Busy making new product, they didn't have time
to figure out "what was up" with the Sub Standard Drives..

At my Employer, we had a period of time, about 5 years ago, where units
that couldn't Quickly be Fixed, after Failing during Production Testing,
went into a Big Box...
It was only last year that our one Tech started Digging Through that box
and Fixing them... He had about Three of Four years experience with our
products at that point... So I can see Shugart with Option #2...

MarkO
Michael J. Mahon
2017-08-30 07:04:04 UTC
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Post by Mark D. Overholser
On Tue, Aug 29, 2017 at 9:22 AM, Mark D. Overholser
<< BIG SNIP >>
Precise Marking and Before and After Pictures...
I have been very curious to know what, "The solution was to optimize
the analog electronics, tighten up the drive adjustment procedures
and build some test fixtures to make adjustments reasonable to do in
<http://www.apple1notes.com/old_apple/Huston_Stories_files/Disk%20SN1.htm>
MarkO
I remember reading the story years ago how Shugart had given Apple
some of their "subpar" drives - funny.
Larry G
I wonder if Shugart
#1 ) Had "trouble" figure out what was wrong with them, or
#2 ) If they were just So Busy making new product, they didn't have time
to figure out "what was up" with the Sub Standard Drives..
At my Employer, we had a period of time, about 5 years ago, where units
that couldn't Quickly be Fixed, after Failing during Production Testing,
went into a Big Box...
It was only last year that our one Tech started Digging Through that box
and Fixing them... He had about Three of Four years experience with our
products at that point... So I can see Shugart with Option #2...
MarkO
It is much more likely that the drive was specified as a 35 track drive.
Exceeding that number of tracks results in smaller diameter, thus higher
bit density, tracks, and conservative design would not push recording
density beyond what media manufacturers would guarantee.

As media quality improved and it was demonstrated that more inner tracks
could be reliably supported, drive manufacturers changed drive
specifications to support more tracks.
--
-michael - NadaNet 3.1 and AppleCrate II: http://michaeljmahon.com
Jorge
2017-08-30 08:46:07 UTC
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Post by Michael J. Mahon
It is much more likely that the drive was specified as a 35 track drive.
Exceeding that number of tracks results in smaller diameter, thus higher
bit density, tracks, and conservative design would not push recording
density beyond what media manufacturers would guarantee.
As media quality improved and it was demonstrated that more inner tracks
could be reliably supported, drive manufacturers changed drive
specifications to support more tracks.
Yes, exactly, I think so too. The Shugart SA390 (*) was really an SA400, and the specs were 109.4 kbytes per disk, 3125 bytes per track, which would => 35 tracks not 40.

(*) An SA 400 without head load actuator solenoid and no sector index detector:

http://www.swtpc.com/mholley/SA400/SA400_Index.htm
--
Jorge.
Mark D. Overholser
2017-08-30 15:32:17 UTC
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On Tue, Aug 29, 2017 at 10:14 PM, Mark D. Overholser
On Tue, Aug 29, 2017 at 9:22 AM, Mark D. Overholser
<< BIG SNIP >>
Precise Marking and Before and After Pictures...
I have been very curious to know what, "The solution was to optimize
the analog electronics, tighten up the drive adjustment procedures
and build some test fixtures to make adjustments reasonable to do in
<http://www.apple1notes.com/old_apple/Huston_Stories_files/Disk%20SN1.htm>
MarkO
I remember reading the story years ago how Shugart had given Apple
some of their "subpar" drives - funny.
Larry G
I wonder if Shugart #1 ) Had "trouble" figure out what was wrong with
them, or #2 ) If they were just So Busy making new product, they
didn't have time to figure out "what was up" with the Sub Standard
Drives..
At my Employer, we had a period of time, about 5 years ago, where
units that couldn't Quickly be Fixed, after Failing during Production
Testing, went into a Big Box... It was only last year that our one
Tech started Digging Through that box and Fixing them... He had
about Three of Four years experience with our products at that
point... So I can see Shugart with Option #2...
MarkO
Did you see my FB pictures about the non-Shugart Disk II's ? I put
more photos of Disk II's that could possibly do 40 tracks if
modified. I don't know if they are "Alps" drives you mentioned? There
is no labeling. It's on the thread where I posted ADTPRO40T.DSK
file. Are Alps drives labeled as Alps ?
Larry G
Yes I did... I would guess that since Alps was a 3rd Party Manufacture,
and they were Cloning the Shugart, they sold the Drives to anyone that
wanted the Shugart, but didn't want to pay the price for a Shugart..

I believe that I read somewhere, that Apple's cost for the Alps was half
the cost of the Shugart. Something like $90.00 verses $160.00...

MarkO
Jorge
2017-09-07 15:51:57 UTC
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Post by retrogear
I have two MicroSci 5.25 drives which are Shugart 390 mechanisms. They look like identical drives except one will format out to 40 tracks but the other stops after 35. Was there a modification to make 40 track work? Seems like I remember that from 30 years ago but lost in the brain fog of time
Hi,

WRT this, today I've learned something new, firstly that the early floppy disks had a window/opening smaller than later ones, that would make it difficult/impossible to format them @40 tracks. Second that Shugart made a later SA400, the SA400L, that was good for 40 tracks. I've opened the disk /// that's connected to my Apple II and... it's an SA400L !!!

This page is priceless:

http://www.retrotechnology.com/herbs_stuff/drive.html#shugart

""The older [35-track media] has a [window] length of 1.210 inches, [from NorthStar DOS] 4.0 distribution media. I have about 40 pieces of media from before mid-1979 that have the smaller hole. All used with hard sector NS MDS [systems]. The [40-track] standard is 1.370 inches I have hard sector and soft sector diskettes that meets that size.

The [hole] width is 0.5 inches for all. From the outer edge of envelope [the hole begins at] 0.13 inches. Then a 1.21 inch opening [for 35 track media]...the standard is 1.37."

"omewhere around 1979-1980 there was a standards change and the window was opened up to accomodate 40 tracks. Right about the same time, the SA-400L (40 track version of the SA-400) was introduced."

Thanks Herb Johnson!

Cheers,
--
Jorge.
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