Hi all,

As mentioned in my PET 8296 repair thread...the 2031LP that came with it has
a strange problem.  It trashes any disk it writes to.  It reads just fine,
even floppies written on other drives, so I think the alignment is fine.
After a write, the disk is unusable until I reformat it on another drive.
Formatting on the 2031LP doesn't work at all, I just get a ?bad disk error.

So, two questions...

1. What failure would cause this to happen?

2. Can the mechanism from a 1541 be installed into the 2031LP?

Thanks,
Leif


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In article <1110234657.d8626a35752b39406e46c537c8189898@teranews>,
Leif Bloomquist <spam@127.0.0.1301> wrote:
>
>As mentioned in my PET 8296 repair thread...the 2031LP that came with it has
>a strange problem.  It trashes any disk it writes to.  It reads just fine,
>even floppies written on other drives, so I think the alignment is fine.
>After a write, the disk is unusable until I reformat it on another drive.
>Formatting on the 2031LP doesn't work at all, I just get a ?bad disk error.
>

  The 1571 in my 128DCR does this too.

  My bet is that a CMOS switch or similar en route from the output shift
register to the head has died.  I haven't done any debugging, though, nor
even looked at the schematics.

-- 
David Evans
Research Assistant Professor
School of Computer Science                     dfevans@bbcr.uwaterloo.ca
University of Waterloo, Canada        http://bbcr.uwaterloo.ca/~dfevans/

"Leif Bloomquist" wrote ...
>
> As mentioned in my PET 8296 repair thread...the 2031LP that came with it
> has a strange problem.  It trashes any disk it writes to.  It reads just
> fine, even floppies written on other drives, so I think the alignment is
> fine.  After a write, the disk is unusable until I reformat it on another
> drive.  Formatting on the 2031LP doesn't work at all, I just get a ?bad
> disk error.

Have you tried looking at a trashed disk with a track & sector editor to see
if only those tracks written to are trashed?  This could include the
directory track because after a file write the BAM is updated, thus a write
on the directory track.
-- 
Best regards,

Sam Gillett

Change is inevitable,
except from vending machines!

"Leif Bloomquist" <spam@127.0.0.1301> writes:

>2. Can the mechanism from a 1541 be installed into the 2031LP?

I don't see why not. They're nearly the same drive.

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  ** Computer Workshops: games, productivity software and more for C64/128! **
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"Leif Bloomquist" <spam@127.0.0.1301> wrote in message
news:1110234657.d8626a35752b39406e46c537c8189898@teranews...
>
> Hi all,
>
> As mentioned in my PET 8296 repair thread...the 2031LP that came with it
has
> a strange problem.  It trashes any disk it writes to.  It reads just fine,
> even floppies written on other drives, so I think the alignment is fine.
> After a write, the disk is unusable until I reformat it on another drive.
> Formatting on the 2031LP doesn't work at all, I just get a ?bad disk
error.
>
> So, two questions...
>
> 1. What failure would cause this to happen?

Possibly the write amplifier circuit?

>
> 2. Can the mechanism from a 1541 be installed into the 2031LP?

Not sure, but if it is a problem with the circuit, this wouldn't really
help.

Scott McDonnell

Leif Bloomquist wrote:
> Hi all,
> 
> As mentioned in my PET 8296 repair thread...the 2031LP that came with it has
> a strange problem.  It trashes any disk it writes to.  It reads just fine,
> even floppies written on other drives, so I think the alignment is fine.
> After a write, the disk is unusable until I reformat it on another drive.
> Formatting on the 2031LP doesn't work at all, I just get a ?bad disk error.
> 
> So, two questions...
> 
> 1. What failure would cause this to happen?

Since reading works and writing at least to some part, I don't think the r/w 
head is damaged. But since it's a quick test, you can hook up a 1541 mech 
just to make sure.

If it's a failure on the circuit board, there's a lot of circuits that are 
involved only in writing to disk. I don't have a 2031LP schematic diagram 
here, but one for the 1540, so I won't quote any component locations here, 
though they might be the same. Suspicious are the disk controller 6522, and 
the 7417 line driver. The others might also fail, but I'd start with these two.

Nicolas

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"Scott McDonnell" <NetSamurai@c0mcast.net> wrote in message
news:loCdndnNGerx3bDfRVn-oQ@comcast.com...

> > 2. Can the mechanism from a 1541 be installed into the 2031LP?

> Not sure, but if it is a problem with the circuit, this wouldn't really
> help.

Oh!  Good point.  Ideally I would replace everything up to the IEEE-488
interface, but I doubt that's possible.

Thanks for all the suggestions everyone, I'll give them a try.

Regards,
Leif