I wish apologize me. the work was done by a dear friend and I had mistakenly understood that he had used the Fluxengine card instead he used this card http://www.pdp8online.com/mfm/ with add-on daughter card interfacing with the SASI controller SA-1403. Since, despite repeated readings, we are not able to correctly extract the data from the second Winchester Hard Disk, we will probably operate by trying to rely on someone able to intervene on the platters of the SA-1004 Hard Disk, hoping to be able to recover as much as possible.
Enrico -----Messaggio originale----- Da: cctech [mailto:cctech-boun...@classiccmp.org] Per conto di David Gesswein via cctech Inviato: giovedì 4 febbraio 2021 01:45 A: cct...@classiccmp.org Oggetto: Re: Winchester SA1004 file recovering On Wed, Feb 03, 2021 at 10:43:48AM +0100, Enrico email.it wrote: > > > A very dear friend first read in raw mode a 10MB Winchester hard disk model > Shugard SA1004 from which the files were correctly extracted and then set up > a test bench from which you can see in this video the complete system > operating with the HD ed il controller Shugart SASI SA1403: > https://www.dropbox.com/s/d9iacfgrnexso3o/GP%20T20%20con%20HD%20banco%20prov > a.mp4?dl=0 > > Despite we having attempted different readings (even using cards from the > first hard disk), using the same FLUXengine card > (http://cowlark.com/fluxengine/doc/building.html) the raw file still does > not present the Hard Disk directory, instead we read the information of the > files present but there may be bad bytes in these files and in the rest of > the disk as well. > I have only heard of FLUXengine being used for floppies. Can it handle hard drives? I hadn't heard of other boards that can read MFM hard drives other than mine http://www.pdp8online.com/mfm/. Other than the drive being faulty the biggest reason reading fails is the heads are no longer on track. You can tell that by looking at a histogram of the flux transition timing for a track. If they show peaks with good nulls between them the data is likely recoverable. If they don't you have to do something to shift the head position. Example histogram from by unit for ST506 type drive. https://groups.google.com/g/mfm-discuss/c/kjKez8vfapU/m/4XamyQJgCAAJ The SA1004 is a stepper drive. Some people have had success on other stepper drives with putting some rotation force or drag on the stepper to shift the heads. Creating a microstepper driver would give better control. May be able to say more if you provide more information on what you have done and checked to try to recover the contents.
