On 3/15/19 9:09 PM, George Rimakis wrote:
Hi all,
Sorry to bombard the list with DVI related posts, but I am having an issue.
So, I have two DVI’s one with two drives, one with one.
At first I used the DVI with one drive, was able to format the boot disk, and
make a copy. After that I am not able to format any additional disks. I just
get a Format Failed error.
I tried the second DVI, and only one of the two drives can format the disks.
They all can read and write to disks that are formatted however.
I took them apart and cleaned the heads with isopropyl, but nothing has changed.
Does any have experience with 180k drives like this being unable to format, but
otherwise appearing fine?
~George
First just make sure you are using SD or DD disks (360K) not HD (1.2M).
Other than that there are many age related failure points on all old
floppy drives.
Make sure all the mechanicals are good obviously.
The rpm adjustment is easy, as there is a strobe sticker on the main
spindle and a trim pot on the spindle motor driver board (there is also
a trim pot on the main board, don't tough that one)
https://photos.app.goo.gl/jbBSq96GExzKCw727
https://photos.app.goo.gl/Ww6o6fXGzDfuTAcP9
For radial alignment, if you have an old 386-486 era machine (so it has
a floppy controller that's old enough) you can try this method using
ImageDisk:
https://www.classic-computers.org.nz/blog/2010-06-28-alignment-tandon-m100.htm
Note this method relies on having a disk that you believe has proper
alignment to start with, to use as a reference. It can't be one you
formatted in the drive previously, or in any other old questionable
drive. Ideally it should be a few different commercially produced disks
that previous owners probably never re-formatted.
That's about all the low hanging fruit other than you could try
replacing the electrolytic caps and just visually inspect traces..
Beyond that you need to know how to actually diagnose electronics to
find components that have gone bad.
Now here's a question for the group...
Drives had to have the radial alignment calibrated very exactly at the
factory using special alignment disks, and then locked down for all time
right?
I wonder if the plastic sheets that all disks are made of have shrunk at
all over 30-40 years, making the *disks* out of alignment, causing
people to take technically proper drives and move them actually out of
the proper spec, so that they can read 40 year old disks??
(Or more specifically, 40 year old formatting. Even if the mylar sheet
has shrunk, it would still format to spec again just fine, by just
formatting it today in a properly aligned drive.)
If this idea is true, then I guess everyone should try to keep one
out-of-spec drive just for reading old disks that you don't want to
reformat. You don't ever format or even write anything with that drive,
it's just for reading and just for really old disks. Then for formatting
and writing you use a properly aligned drive.
And, if this idea of the mylar shrinking is true, does that mean that
even if you had one of the original special factory calibration
reference discs, that probably means that disk is no longer a good
reference. It would be shrunk out of spec too. We'd have to come up with
a new reference.
--
bkw
