20 Aug
2015
20 Aug
'15
4:04 p.m.
Following Chuck's advice, I scoped out the pin 22 and 24 (write data and
write gate) on the floppy, and they looked fine. Then being curious, I
managed to figure out what the write wire for Head 0 was. And I discovered I
got nice matching writing pulses at 300 kHz (formatting at 360k density),
but none at 500 kHz (1.2 Mb density). Results posted here:
http://www.vintage-computer.com/vcforum/showthread.php?43874-5-1-4-quot-Flop
py-Drive-Not-Reading/page9
So I tried to force formatting in DOS at 360k, and sure enough it worked! I
can then read the diskette back, write on it, etc... And of course it failed
formatting at 1.2 Mb. But the drive (Chinon FR-506) is a 1.2M one, and reads
fine at 1.2M! Any clue? Is there a drive setting that would prevent it to
write at high density but let it do at low density?
Marc
Date: Tue, 18 Aug 2015 21:30:31 -0700
From: cclist at sydex.com
To: cctalk at classiccmp.org
Subject: Re: 5.25 floppies that read but don't write
On 08/18/2015 09:05 PM, Marc Verdiell wrote:
I have connected a 1.2M 5.25" floppy to my computer. After a bit of
jumper learning and setting, it's recognized and reads my old DD and
HD floppies fine. But for the life of me I cannot write to it. Not
under DOS, Win98, or WindowsXP. Which all read fine.
Make sure that "WRITE GATE" goes low (use a logic probe) on pin 24 of
the drive while you do your write. If so, your floppy write circuitry
has a problem. I.e., it's not the cable.
--Chuck
20 Aug
20 Aug
4:57 p.m.
On 08/20/2015 01:04 PM, Marc Verdiell wrote:
So I tried to force formatting in DOS at 360k, and
sure enough it
worked! I can then read the diskette back, write on it, etc... And of
course it failed formatting at 1.2 Mb. But the drive (Chinon FR-506)
is a 1.2M one, and reads fine at 1.2M! Any clue? Is there a drive
setting that would prevent it to write at high density but let it do
at low density?
At high density, have you taken a good look at pin 2 of the floppy
interface? Have you checked to see if pin 2 is configured (via jumpers)
as "density select"? Various drives have different jumperings for
pins 2 and 34 (and sometimes 4). For example, I deal with some Japanese
CNC gear that uses pin 2 for disk change and pin 34 for read (and pin 4
for "in use".
--Chuck
11:01 p.m.
Date: Thu, 20 Aug 2015 13:57:05 -0700
From: cclist at sydex.com
To: General at classiccmp.org; classiccmp.org:On-Topic and Off-Topic Posts cctalk at
classiccmp.org
Subject: Re: 5.25 floppies that read but don't write
On 08/20/2015 01:04 PM, Marc Verdiell wrote:
If formatting an already formatted disk, the format program will notlet you format
a different density.Do note what I said earlier. Just formatting and writing to a 360K ona
1.2M drive can in some cases make it unusable on a 360K drive.The 1.2M drive does not
erase the full width of a 360K track.When attempting to read on a 360K drive, there will
be too much noisefrom the older track.If you are really interested in creating 360K disk,
you must have a 360Kdrive.Dwight
So I tried to force formatting in DOS at 360k,
and sure enough it
worked! I can then read the diskette back, write on it, etc... And of
course it failed formatting at 1.2 Mb. But the drive (Chinon FR-506)
is a 1.2M one, and reads fine at 1.2M! Any clue? Is there a drive
setting that would prevent it to write at high density but let it do
at low density?
At high density, have you taken a good look at pin 2 of the floppy
interface? Have you checked to see if pin 2 is configured (via jumpers)
as "density select"? Various drives have different jumperings for
pins 2 and 34 (and sometimes 4). For example, I deal with some Japanese
CNC gear that uses pin 2 for disk change and pin 34 for read (and pin 4
for "in use".
--Chuck
11:35 p.m.
On Thu, Aug 20, 2015 at 9:01 PM, dwight <dkelvey at hotmail.com> wrote:
If you are really interested in creating 360K disk,
you must have a 360Kdrive.
And beyond that, sometimes trying to format or write to a "360K" (48
TPI) disk in a "1.2M" (96 TPI) drive does appear to work, and may even
appear to read reliably on the same drive, but it's *NEVER* going to
be reliable to read it on an actual 48 TPI drive.
The best case result is if you use a 96 TPI drive with a floppy that
has NEVER been written (even at the factory), and format it and write
at 48 TPI, that actually may read reliably on 48 TPI drives, because
it doesn't have remnants of normal-width 48 TPI tracks. However, it's
still not recommended for obvious reasons.
Some people have claimed that they've been able to achieve the same
effect by degaussing the floppy first, but when I experimented with
that I found that even a supposedly high-power degaussing coil was
pretty marginal for actually erasing floppy disks. It definitely would
corrupt the data and render it unreadable, but it did NOT yield a
truly erased disk.
21 Aug
21 Aug
12:46 a.m.
Re: Degaussing floppies.
Only part of degaussing a floppy is getting a strong enough degausser--I
use on made for wiping VHS carts--it gets very hot after only about 3
minutes of use and the thermal cutout belays my impatience until it
cools off. So it's definitely not wimpy.
However, to use it, you have to observe the correct mumbo-jumbo. You
press it against the floppy in question, hit and hold the power button
and *slowly* pull the disk away, moving said disk in a roughly circular
motion.
A quick check using Kyread shows no discernible magnetic pattern remaining.
On a related matter, I've found that using a very strong rare
earth/neodymium magnet (i.e. if you get your fingers between it and a
hunk of iron, you should not be surprised with broken bones or severe
tissue damage) on a "bad" high-density 3.5" floppy, followed by a pass
with the degausser will often return the floppy to usability. This
comes up occasionally when I'm asked to repair a factory-labeled floppy
that's developed issues. You want to keep the original labeling and
short of inserting a new "cookie", this approach actually works.
For what it's worth, I use the magnets with large steel ball bearings to
roll dents out of sheet brass--so I do have a valid reason for having
one around.
This goes to an observation that DSHD 3.5" media appears to develop some
sort of "fatigue" after a certain number of write passes.
For what little it's worth,
Chuck
3264
days inactive
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