5 Feb
2016
5 Feb
'16
1:58 p.m.
I have two intermittently functional 8" floppy drives that I debugged
to the best of my ability, and as far as I've been able to tell their
problems must be limited to the circuitry that deals with the actual
magnetic interface with the disk. The intercommunication seems normal
and the head load solenoids fire, but after that the drive often
aborts the process, presumably because it wasn't able to read data
properly. I think the signal for reading the disk-rotation hole even
fires correctly.
The drives are Siemens FDD 100-8 drives used in an S-100 bus system,
and controlled by a Jade "Double D" disk controller. The machine was
in a functional state when stored, and I have known-good copies of
disks that I've been able to boot from at least a few times. (Unless
the drives somehow damaged them.)
Can someone knowledgeable about 8" floppy drives share information
about how these things were serviced and maintained, and what sort of
procedures were required to test and calibrate them?
Information I've picked up through osmosis leads me to believe that
there's a floppy disk with a special pattern on it, and you use
specialized test equipment to check the flux off the head and dial it
into proper settings. I suspect there the drive has trim pots or
similar that allow for this.
So, how do you deal with your 8" drives, and what do you do when they
don't work?
Thanks,
Dan
5 Feb
5 Feb
3:40 p.m.
On 02/05/2016 01:58 PM, Dan K wrote:
So, how do you deal with your 8" drives, and what
do you do when
they don't work?
I've got both the FDD-100s and the double-sided cousin, the FDD-200.
They're very similar in construction; good German engineering, cast
metal faceplates, etc. They really should not be drifting out of
alignment. Bitsavers has some useful documents on them.
First off, IIRC, these are leadscrew-type positioner drives. One issue
dogging these is that grease on the leadscrew can get filthy with dirt
or harden, preventing smooth operation of the positioner. Make sure
that the leadscrew is clean--use a mild solvent such as kerosene if it's
hardened. Re-lube with a lightweight grease or oil--you just don't want
the carriage to "stick" in its travel.
Make sure that the track 0 sensor is clean--the same for the index sensor.
Remember that floppy drive bus topology is open-collector, which implies
that the "receiving" (far) end be terminated with a pullup resistor
(usually 150 ohms to +5 on 8" drives). Very often, this is in the form
of a DIP resistor network. If you're missing it, operation is going to
be erratic.
Since you're dealing with single-sided floppies, check the condition of
the side 1 pressure pad--the glue on these often dries out and the pad
falls off. The pad itself resembles a billiard cue tip.
Don't get into the alignment issue without a scope and an alignment
disk--once you loosen the stepper motors, it's a very touchy operation
getting them back into position, even with a special (expensive)
alignment disk.
Hopefully, this will get you started. Just remember that dirt in any
disk drive is the Devil's playground.
--Chuck
5:03 p.m.
If belt driven ( suspect most 8 incher are ), make sure
the pulleys are smooth and clean.
Often old belts will lose a little small lump of rubber that
stick to the pulley. This will cause mis-reads.
Make sure the belt is tight and not slipping.
The pressure pad can get lumps on it from disk crud.
The pad must be flat. It can not be cleaned with a
clear disk that is double sided.
Solvents don't work well. I often find a dull knife edge works
well to get crusted gunk off.
The rest, Chuck had stated. Don't mess with
tracking or fiddle with pots that you are not setup properly
to adjust.
Dwight
________________________________________
From: cctalk <cctalk-bounces at classiccmp.org> on behalf of Chuck Guzis <cclist
at sydex.com>
Sent: Friday, February 5, 2016 3:40 PM
To: General Discussion: On-Topic and Off-Topic Posts
Subject: Re: Calibration of 8" floppy drive?
On 02/05/2016 01:58 PM, Dan K wrote:
So, how do you deal with your 8" drives, and what
do you do when
they don't work?
I've got both the FDD-100s and the double-sided cousin, the FDD-200.
They're very similar in construction; good German engineering, cast
metal faceplates, etc. They really should not be drifting out of
alignment. Bitsavers has some useful documents on them.
First off, IIRC, these are leadscrew-type positioner drives. One issue
dogging these is that grease on the leadscrew can get filthy with dirt
or harden, preventing smooth operation of the positioner. Make sure
that the leadscrew is clean--use a mild solvent such as kerosene if it's
hardened. Re-lube with a lightweight grease or oil--you just don't want
the carriage to "stick" in its travel.
Make sure that the track 0 sensor is clean--the same for the index sensor.
Remember that floppy drive bus topology is open-collector, which implies
that the "receiving" (far) end be terminated with a pullup resistor
(usually 150 ohms to +5 on 8" drives). Very often, this is in the form
of a DIP resistor network. If you're missing it, operation is going to
be erratic.
Since you're dealing with single-sided floppies, check the condition of
the side 1 pressure pad--the glue on these often dries out and the pad
falls off. The pad itself resembles a billiard cue tip.
Don't get into the alignment issue without a scope and an alignment
disk--once you loosen the stepper motors, it's a very touchy operation
getting them back into position, even with a special (expensive)
alignment disk.
Hopefully, this will get you started. Just remember that dirt in any
disk drive is the Devil's playground.
--Chuck
6:02 p.m.
First off, IIRC, these are leadscrew-type positioner
drives. One issue dogging these is that grease on the leadscrew can get filthy with dirt
or harden, preventing smooth operation of the positioner. Make sure that the leadscrew is
clean--use a mild solvent such as kerosene if it's hardened. Re-lube with a
lightweight grease or oil--you just don't want the carriage to "stick" in
its travel.
Good point about this. One drive was quite smooth on that long lead
screw, the other was very stiff. I thought that it was trying to move
it and drawing too much current, leading to a shutdown or error state.
It loosened up with manual turning and I used some light machine oil
and worked it in. It now moves about as easily as the other, so I
don't think that this is still the issue.
Make sure that the track 0 sensor is clean--the same
for the index sensor.
I believe I probed these with my oscilloscope and verified they were
toggling, but it wouldn't hurt to check again.
Remember that floppy drive bus topology is
open-collector, which implies that the "receiving" (far) end be terminated with
a pullup resistor (usually 150 ohms to +5 on 8" drives). Very often, this is in the
form of a DIP resistor network. If you're missing it, operation is going to be
erratic.
Another great tip. This plagued me for a long time, until I realized
that I had only one drive connected, and it had the resistor network
IC unpopulated. I borrowed it from the other drive (they were on the
same wire, so I suppose that only one resistor network is necessary)
and that's what led to my initial success.
Since you're dealing with single-sided floppies,
check the condition of the side 1 pressure pad--the glue on these often dries out and the
pad falls off. The pad itself resembles a billiard cue tip.
You're going right down the list of issues I ran into! One of the
pressure pads was nonexistent, but the other is in good condition. One
issue I had was that the head load plastic assembly that brings the
media in conformity with the sensor was broken and held together with
a twisty-tie. I used some CAD software to design a replacement and had
it 3D printed:
http://www.vintage-computer.com/vcforum/showthread.php?49265-Owning-and-ope…
It seems to do the job, but I still don't have a replacement pad. That
seems to be okay however, because on one drive the head load solenoid
doesn't appear to come down far enough to push the disk very much. I
don't think I've ever seen the pad on either drive come down enough to
physically touch the disk--maybe just brushing it, barely. What might
cause this?
-Dan
On 2/5/16, dwight <dkelvey at hotmail.com> wrote:
If belt driven ( suspect most 8 incher are ), make
sure
the pulleys are smooth and clean.
Often old belts will lose a little small lump of rubber that
stick to the pulley. This will cause mis-reads.
Make sure the belt is tight and not slipping.
The pressure pad can get lumps on it from disk crud.
The pad must be flat. It can not be cleaned with a
clear disk that is double sided.
Solvents don't work well. I often find a dull knife edge works
well to get crusted gunk off.
The rest, Chuck had stated. Don't mess with
tracking or fiddle with pots that you are not setup properly
to adjust.
Dwight
________________________________________
From: cctalk <cctalk-bounces at classiccmp.org> on behalf of Chuck Guzis
<cclist at sydex.com>
Sent: Friday, February 5, 2016 3:40 PM
To: General Discussion: On-Topic and Off-Topic Posts
Subject: Re: Calibration of 8" floppy drive?
On 02/05/2016 01:58 PM, Dan K wrote:
So, how do you deal with your 8" drives, and
what do you do when
they don't work?
I've got both the FDD-100s and the double-sided cousin, the FDD-200.
They're very similar in construction; good German engineering, cast
metal faceplates, etc. They really should not be drifting out of
alignment. Bitsavers has some useful documents on them.
First off, IIRC, these are leadscrew-type positioner drives. One issue
dogging these is that grease on the leadscrew can get filthy with dirt
or harden, preventing smooth operation of the positioner. Make sure
that the leadscrew is clean--use a mild solvent such as kerosene if it's
hardened. Re-lube with a lightweight grease or oil--you just don't want
the carriage to "stick" in its travel.
Make sure that the track 0 sensor is clean--the same for the index sensor.
Remember that floppy drive bus topology is open-collector, which implies
that the "receiving" (far) end be terminated with a pullup resistor
(usually 150 ohms to +5 on 8" drives). Very often, this is in the form
of a DIP resistor network. If you're missing it, operation is going to
be erratic.
Since you're dealing with single-sided floppies, check the condition of
the side 1 pressure pad--the glue on these often dries out and the pad
falls off. The pad itself resembles a billiard cue tip.
Don't get into the alignment issue without a scope and an alignment
disk--once you loosen the stepper motors, it's a very touchy operation
getting them back into position, even with a special (expensive)
alignment disk.
Hopefully, this will get you started. Just remember that dirt in any
disk drive is the Devil's playground.
--Chuck
7:52 p.m.
On 02/05/2016 08:02 PM, Dan K wrote:
Another great tip. This plagued me for a long time,
until
I realized that I had only one drive connected, and it had
the resistor network IC unpopulated. I borrowed it from
the other drive (they were on the same wire, so I suppose
that only one resistor network is necessary) and that's
what led to my initial success.
Yes, the terminating resistor pack should only be
in the
last drive on the cable.
It seems to do the job, but I still don't have a
replacement pad. That seems to be okay however, because on
one drive the head load solenoid doesn't appear to come
down far enough to push the disk very much. I don't think
I've ever seen the pad on either drive come down enough to
physically touch the disk--maybe just brushing it, barely.
What might cause this?
Probably wear, or maybe warpage of the parts over time. The
pressure pad should be fairly soft, usually a felt-like
material. It needs to push the media into contact with the
read-write head. Without it, you will occasionally get good
enough contact to read a sector header or even a whole
sector, but it won't be consistent. The data will come and
go as the disk rotates.
Jon
9:46 p.m.
Are there any good alternative solutions I can do to replace it? I'm
sure I don't want the plastic touching the disk media.
-Dan
On 2/5/16, Jon Elson <elson at pico-systems.com> wrote:
On 02/05/2016 08:02 PM, Dan K wrote:
Another great tip. This plagued me for a long
time, until
I realized that I had only one drive connected, and it had
the resistor network IC unpopulated. I borrowed it from
the other drive (they were on the same wire, so I suppose
that only one resistor network is necessary) and that's
what led to my initial success.
Yes, the terminating resistor pack should only be
in the
last drive on the cable.
It seems to do the job, but I still don't
have a
replacement pad. That seems to be okay however, because on
one drive the head load solenoid doesn't appear to come
down far enough to push the disk very much. I don't think
I've ever seen the pad on either drive come down enough to
physically touch the disk--maybe just brushing it, barely.
What might cause this?
Probably wear, or maybe warpage of the parts over time.
The
pressure pad should be fairly soft, usually a felt-like
material. It needs to push the media into contact with the
read-write head. Without it, you will occasionally get good
enough contact to read a sector header or even a whole
sector, but it won't be consistent. The data will come and
go as the disk rotates.
Jon
6 Feb
6 Feb
7:23 a.m.
On Feb 5, 2016, at 21:46, Dan K <100dashsix at
gmail.com> wrote:
Are there any good alternative solutions I can do to replace it? I'm
sure I don't want the plastic touching the disk media.
I'm assuming that you are asking about replacing the pressure pad. My usual source for
felt material is McMaster-Carr. I don't know which composition and hardness are best
for this application, though. They carry both wool felt and synthetic felt.
https://www.mcmaster.com
--
Mark J. Blair, NF6X <nf6x at nf6x.net>
http://www.nf6x.net/
9:29 a.m.
On 02/05/2016 11:46 PM, Dan K wrote:
Are there any good alternative solutions I can do to
replace it? I'm
sure I don't want the plastic touching the disk media.
Probably the pressure pad in an audio cassette is about the
same material. Depending on how large a diameter the floppy
drive's pad was, one from a cassette might not be big enough.
Jon
9:40 a.m.
On 02/05/2016 09:46 PM, Dan K wrote:
Are there any good alternative solutions I can do to
replace it? I'm
sure I don't want the plastic touching the disk media.
Got any chums in the musical instrument repair business? Wind
instruments (woodwind and brass) use a fair amount of very high-quality
wool felt and a dot the size of a pressure pad should be easy to come by.
I've even heard of people using the felt pads sold in hardware stores as
cabinet door bumpers or padding for the bottom of table lamps and such.
--Chuck
10:18 a.m.
> Are there any good alternative solutions I can do
to replace it? I'm
> sure I don't want the plastic touching the disk media.
On Sat, 6 Feb 2016, Chuck Guzis wrote:
Got any chums in the musical instrument repair
business? Wind instruments
(woodwind and brass) use a fair amount of very high-quality wool felt and a
dot the size of a pressure pad should be easy to come by.
D'ya mean a tuba spit-valve pad?
I've even heard of people using the felt pads sold
in hardware stores as
cabinet door bumpers or padding for the bottom of table lamps and such.
Most of those are too thin and hard
11:26 a.m.
On 02/06/2016 10:18 AM, Fred Cisin wrote:
D'ya mean a tuba spit-valve pad?
No, those are cork, not felt. On brasswinds, felt's usually used as a
cushioning device on piston valves, so things don't go "clank clank".
Rotary valves employ cork or rubber for a similar use. Pianos use a
great deal of felt.
You might even be able to round up a strip of felt from a laser printer
fuser assembly--used to wipe the fuser drum.
But see, for example, something from Ferree's:
http://www.ferreestools.com/cork-felt/felt.html
--Chuck
3:17 p.m.
A lot of good information here, and I have a music store near me that
I might be able to find a suitable felt or wool pad from. If not
there, then perhaps at Home Depot or online.
Was it uncommon to use floppy disks formatted in other 8" drives in a
machine like this? When someone (very charitably!) gave me this
machine he also provided me with copies of the disks it came with,
presumably from drives that would be compatible.
Let's say that I had a machine with just blank floppy disks, however,
and nothing more than a system monitor ROM that lets me read/write
memory. How could I go from this zero state to running software from a
floppy? Is it easy to write arbitrary bytes to a floppy, so that I
could write a small shim program to read from serial and write to the
floppy? Then I could transfer the disk image over the wire, write it,
then read from it.
Thanks,
Dan
On 2/6/16, Chuck Guzis <cclist at sydex.com> wrote:
On 02/06/2016 10:18 AM, Fred Cisin wrote:
D'ya mean a tuba spit-valve pad?
No, those are cork, not felt. On brasswinds, felt's usually used as a
cushioning device on piston valves, so things don't go "clank clank".
Rotary valves employ cork or rubber for a similar use. Pianos use a
great deal of felt.
You might even be able to round up a strip of felt from a laser printer
fuser assembly--used to wipe the fuser drum.
But see, for example, something from Ferree's:
http://www.ferreestools.com/cork-felt/felt.html
--Chuck
5 Feb
5 Feb
6:05 p.m.
If belt driven ( suspect most 8 incher are ), make sure
the pulleys are smooth and clean.
Often old belts will lose a little small lump of
rubber that stick to
the pulley. This will cause mis-reads. Make sure the belt is tight and
not slipping.
Hmm I think the pulley mechanism seemed okay, but I'll check for dirt
and make sure the rubber seems to be sitting properly.
The pressure pad can get lumps on it from disk crud.
The pad must be flat. It can not be cleaned with a clear disk that is double sided.
Solvents don't work well. I often find a dull knife edge works well to get crusted
gunk off.
Is this the fuzzy little pad that is on the end of the plastic
mechanism that pushes down on the disk? I feel like a knife would cut
the fuzzy material, and one of the pads is missing for me (see above)
The rest, Chuck had stated. Don't mess with
tracking or fiddle with pots that you are not setup properly to adjust.
I'd definitely like to avoid that. Especially for any mechanism that
has a paint marking indicating it was calibrated at the factory
-Dan
On 2/5/16, dwight <dkelvey at hotmail.com> wrote:
If belt driven ( suspect most 8 incher are ), make
sure
the pulleys are smooth and clean.
Often old belts will lose a little small lump of rubber that
stick to the pulley. This will cause mis-reads.
Make sure the belt is tight and not slipping.
The pressure pad can get lumps on it from disk crud.
The pad must be flat. It can not be cleaned with a
clear disk that is double sided.
Solvents don't work well. I often find a dull knife edge works
well to get crusted gunk off.
The rest, Chuck had stated. Don't mess with
tracking or fiddle with pots that you are not setup properly
to adjust.
Dwight
________________________________________
From: cctalk <cctalk-bounces at classiccmp.org> on behalf of Chuck Guzis
<cclist at sydex.com>
Sent: Friday, February 5, 2016 3:40 PM
To: General Discussion: On-Topic and Off-Topic Posts
Subject: Re: Calibration of 8" floppy drive?
On 02/05/2016 01:58 PM, Dan K wrote:
So, how do you deal with your 8" drives, and
what do you do when
they don't work?
I've got both the FDD-100s and the double-sided cousin, the FDD-200.
They're very similar in construction; good German engineering, cast
metal faceplates, etc. They really should not be drifting out of
alignment. Bitsavers has some useful documents on them.
First off, IIRC, these are leadscrew-type positioner drives. One issue
dogging these is that grease on the leadscrew can get filthy with dirt
or harden, preventing smooth operation of the positioner. Make sure
that the leadscrew is clean--use a mild solvent such as kerosene if it's
hardened. Re-lube with a lightweight grease or oil--you just don't want
the carriage to "stick" in its travel.
Make sure that the track 0 sensor is clean--the same for the index sensor.
Remember that floppy drive bus topology is open-collector, which implies
that the "receiving" (far) end be terminated with a pullup resistor
(usually 150 ohms to +5 on 8" drives). Very often, this is in the form
of a DIP resistor network. If you're missing it, operation is going to
be erratic.
Since you're dealing with single-sided floppies, check the condition of
the side 1 pressure pad--the glue on these often dries out and the pad
falls off. The pad itself resembles a billiard cue tip.
Don't get into the alignment issue without a scope and an alignment
disk--once you loosen the stepper motors, it's a very touchy operation
getting them back into position, even with a special (expensive)
alignment disk.
Hopefully, this will get you started. Just remember that dirt in any
disk drive is the Devil's playground.
--Chuck
6 Feb
6 Feb
6:36 a.m.
So, how do you
deal with your 8" drives, and what do you do when
they don't work?
Don't get into the alignment issue without a scope and an alignment
disk--once you loosen the stepper motors, it's a very touchy operation
getting them back into position, even with a special (expensive)
alignment disk.
3242
days inactive
3243
days old
14 comments
8 participants
participants (8)
-
100dashsix＠gmail.com -
ard＠p850ug1.demon.co.uk -
cclist＠sydex.com -
cisin＠xenosoft.com -
dkelvey＠hotmail.com -
elson＠pico-systems.com -
js＠cimmeri.com -
nf6x＠nf6x.net