Re: Tips for making Twiggy images

Hi everyone,

Hopefully I've now obtained a successful image of Disk 3 of the Pascal Workshop v1.0. I've put it online here:

https://drive.google.com/open?id=0B0_fWRp3VVS4Qll2U0FyMnk1a2c&authuser=0

My only basis for saying that the read was successful is the fact that BLU managed to read each sector successfully, or at least that's what I interpret its messages to say.

Several sectors on both sides were marked as "** Difficult". One in particular was marked with "<- ****** Error".

After a bit of futzing around with the option to vary the disk speed, the happy message "<- == Vary Speed Succeeded" appeared. This is surely due to luck more than skill---I am pretty sure that I hit the wrong key on several occasions. A few more "Difficult" sectors were read after that, but the rest of the disk loaded normally.

You can see a complete log from the BLU read operation here:

https://drive.google.com/open?id=0B0_fWRp3VVS4d196WDlLWnRBbXc&authuser=0

I hope that the experts can confirm that this log indicates a successful read.

(More details)

Prior to attempting the copy, I went ahead and tried to clean away some of the dust on the disk. These efforts did not seem to help much, and the term "dust" seems not to have been accurate to characterize the kind of degradation seen on the media surface.

I removed the media from the disk jacket first, and sprayed it with air from a compressed gas duster (e.g. "DustOff"). This seemed not to do anything. (Dunno if it matters, but chemistry buffs might want to ponder the can's warning about how the gas contains 1,1-difluoroethane <http://en.wikipedia.org/wiki/1,1-Difluoroethane>. No idea whether disk media has any particular sensitivity to that chemical.)

Several of you mentioned wiping dust from disks with a damp lint-free cloth. I attempted techniques like this on a single side of the media, the one that seemed to be more dramatically affected by the degradation.

First, I placed lens paper over an affected portion of the media surface. (Nearly all of the visible degradation appeared on the parts of the media that had been at the location of the four r/w head apertures.) Using a straw as a pipette, I dripped distilled water onto the lens paper, in hopes of getting dust to cling to the moistened paper. After wetting, I carefully lifted the paper. No dust was visible there, and the surface looked unchanged (albeit moist). I used the spray duster to dry the media. Spots on the media where water had dried were visible.

Next, I attempted to lightly brush away some of the dust with a damp cloth. Both moist lens paper and moist AlphaLite wipers <http://www.texwipe.com/store/p-696-alphalite.aspx> appeared to lighten the appearance of the degraded area, although they also seemed to leave small scratches in the media surface regardless. No residue appeared on the lens paper or on the cloth.

I noticed after this that the surface of degraded area appeared to dry more rapidly than other areas did. This may have been due to absorption of the water into the media in those places, or perhaps to the media surface becoming more hydrophobic there (think RainX).

After all this had finished, I placed the media into a "clean" jacket and performed the BLU read process described above. I did not attempt to verify the read, to read the disk more than once, or to read it on more than one drive. After reading, the media surface looked to have been scoured or polished by the read heads (or perhaps the foam pads opposing the heads). The degraded regions were still visible beneath the scour.

My concluding hypotheses are as follows:

1. The "dust" apparent on my Pascal 3 disk wasn't really dust: it wasn't really dissociating from the disk surface like ordinary dust would. Instead, I expect it was probably a more gummy substance.
2. Even "scratch free" cloths can still cause scratches.
3. To the extent that I was able to recover data from this disk, it was more luck than anything, and my actions probably did more harm than good. Hopefully not too much harm.

We'll see how it went when I try to install the Workshop from copies of the Twiggies. I'll need to clean the heads of the drive I used to make the image before I attempt this (and perhaps the foam pads as well?). For now, I've been attempting to format a known-bad scratch disk in the drive, just to get something moving in front of the heads. Lens paper and alcohol will come later.

--Tom

On Sunday, January 25, 2015 at 1:43:53 PM UTC-5, Tom Stepleton wrote:
>
> Hi LisaListers,
>
> I took a chance the other day and bought an unopened 1.0 edition of the
> Pascal Workshop. I intend to open it once it arrives; since they aren't
> online yet, it'll be good to scan those manuals and hopefully get some disk
> images.
>
> (I don't know if there are disk images of the released 1.0 workshop on
> bitsavers; there's a set of images called "wshp84" in
> /bits/Apple/Lisa/monitor, with "26 April 84" and "backup" showing on the
> pictures of the disk label, so it certainly could be a real copy instead of
> some Apple-internal prerelease, perhaps serialized.)
>
> In any case, the Twiggies inside the box are surely of official Apple
> FileWare manufacture, which means that the magnetic media may have degraded
> somewhat already; such are the risks of buying unopened.
>
> From previous discussions on this list, it sounds like some of you
> archivists may have managed some successful reads of disks with some
> degradation. What were your techniques? How did you deal with some of the
> material accumulating on drive heads and pads?
>
> Thanks for any guidance,
> --Tom
>

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