Re: CBM-900 floppy disk format/encoding

On 2011-10-28 18:09, MikeS wrote:
>> ... I did have time to open up the CBM-900 and had a look inside.
>> Also I opened a SFD-1001 just to verify my theory that the CBM-900 uses
>> drive that is mechanical identical with the one inside SFD-1001.
>>
>> And I was right the drive in the CBM-900 is completely identical with the
>> one inside a SFD-1001.
>>
>> From that I'll dare to conclude that the CBM-900 floppy disks are
>> DS/QD/100 TPI.
>>
> Well, that would seem to settle the question then although the answer to
> your original question is effectively the same, i.e. you're using the wrong
> type of drive with Kryoflux. Are the drive mechanism model numbers the same
> by any chance? It is still remotely possible that they look the same but
> are
> in fact different mechanically/electrically.

The system is not located at my home and I've only got about one or two 
spare evenings per week to work on it - with so many suggestions and 
things to try out.

It is almost for sure not a 100 TPI drive that is attached to my 
kryoflux. I've used it for dumping both 35 track C64 5.25" floppies and 
80 track Amiga 5.25" floppies. And that it 48 TPI and 96 TPI and I guess 
that a 100 TPI would be able to read that...

I didn't have time to actually check the type of drive attached to the 
kryoflux this time - will try that next week.


>
> Do
> you actually have a running system? If you do, it should be easy to
> determine the real capacity.
>

The system is well preserved and looks fine. But time will tell.
I guess that the system have been powered off for more that 20 years 
now. The power supply needs a checkup in order to make sure that is does 
not blow the components away. A vario trafo (variable transformer) will 
be applied in order to be able to slowly increase the power while 
preserving the sinus curve on the secondary side. This usually prevents 
old capacitors from blowing off.

> I think that most if not all of Commodore's LP QD disk drives were made by
> Panasonic with custom electronics on a more or less standard mechanism;
> if so, perhaps it would be possible to replace the analog board with a
> standard interface version from another Panasonic drive which might then be
> compatible with a PC and Kryoflux.
>

If I remember correctly from last evening the SFD-1001 and CBM-900 
drives were both Matsushita ones...
The challenge in respect to use these drives with a kryoflux is that the 
drives are only mechanics - no amplifier circuitry or anything what so 
ever. The only thing coming out of these drives are something like eight 
or ten wires. Basically it is a stepper, two disk heads and some sensors 
with wires attached to. But I guess that it is possible to wire up some 
circuit that will make the kryoflux think that it is dealing with an 
ordenary drive. But I guess that with the limited time I have available 
it will take me some weeks to make it work :-)

/Uffe



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