Re: Need an 8280 formatted 8" disk

On Mon, Feb 13, 2017 at 10:54 AM, Rob Clarke <crock@clarke-family.org.uk> wrote:
> Thanks Ethan, I have no other 8" drives other than this one, and only 2
> disks of unknown status.

That does make it harder.

> Yes, I've considered writing such a program to step the drive etc, but as
> the ROM of the 8280 is not documented and is AFAIK, unique in using a WD
> FD1797B-02 controller, I simply don't know how without a large amount of
> effort to disassemble the ROMS.

I wasn't suggesting going to that point, rather a simple BASIC program
to do a "B-R" command for blocks on different tracks which _should_
cause the drive to seek, then fail as the media under the head lacked
the correct format to produce meaningful results.  So it _would_
"fail", but the head would at least move around.

>> In case there is a problem with the heads, is the drive mech of a type
>> that can be tested on another platform?  (Tandon TM848, for example,
>> which the photo resembles)

I looked into ftp://www.zimmers.net/pub/cbm/schematics/drives/old/8280/index.html
 It _is_ a Tandon TM-848.  That is an easy one to hook up to a
"modern" machine, and for reads, you wouldn't need a "TG43" signal
generator (though this, from John Wilson, would take care of
everything including 50 pin<->34 pin wiring
http://www.dbit.com/fdadap.html)  If you did pull one of the drives
from the 8280, it could be hooked up to a PC and used as an 8" drive -
there are formatting programs, etc., out there for such use.  this
would only get you the IBM 250K MFM format, but that's supposed to be
supported on the 8280, so I _think_ one would do OPEN
15,8,15,"N0:MYDISK" to not format the media, but write out a BAM and
directory track).  A valid but admittedly intermediate test to
formatting the whole thing.

Oh... and since it's a dual drive, I'd also consider OPEN
15,8,15,"N1:MYDISK,XX" and if that failed the same way, I would
probably proceed under the expectation that both drive mechs are
probably not faulty in the same way.

Sounds like you have someone to send you an 8280 disk so you may be
all set, but I'd be impatient enough to at least fiddle with something
to read blocks on different tracks just to ensure the FD1797 FDC is at
least nominally happy.  Of course that won't test read/write and data
sep circuits or the TM848 heads, but it would test everything up to
that point.

-ethan

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