PC diskette drives in a HP 9122C was WTB: HP-85 16k RAM Module and HPIB Floppy Drive

[Chuck Guzis]

On 11/23/2017 07:02 PM, Paul Berger via cctalk wrote:
> I have managed to get 2 PC type drives working in a 9122C they are two
> different versions of the YE Data YD-702D.  The important thing is the
> drive needs to provide a ready signal, diskette change and density. 
> Most drives provide the last two but do not have a ready signal.  You
> also need to leave pin 1 unconnected this is a signal from the
> controller to reset the diskette changed signal.  One of the drive the
> YD-702D-6037 can also be altered by moving jumpers to get power from the
> cable.  The other a YD-702D-6537D does not and it unfortunately seems to
> be the more common drive.  I changed the drives so that ready is on Pin
> 34, diskette change on pin 2 and density on pin 4, the same as the Sony
> drive in the 9122C.  I did encounter one problem where if I tried to CAT
> a diskette it would always report that the diskette was changed or
> missing and I recall encountering this previously, it may be related to
> how the diskette changed signal gets reset. On most "standard" 3.5"
> drives the diskette changed signal gets reset as soon as the drive is
> selected and receives a step pulse. On the Sony drives used in the 9122C
> reset the diskette changed signal by a pulse on pin 1 from the
> controller.  What I think is happening is when media is changed, the
> controller thinks it does not have to move the head so the diskette
> changed never gets reset so the controller continues to think the
> diskette has been changed, I will do more testing to verify.  I thought
> that booting with the drive empty provoked this but that is not the
> case.  I can post details of the modifications to the drives if anyone
> is interested.

In cases like this, I fall back to my favorite--the Samsung SFD-321B:

http://www.techtravels.org/wp-content/uploads/pefiles/SAMSUNG-SFD321B-070103.pdf

Plenty of them in the wild and very configurable.   In most of my cases,
pin 34 is ready, pin 2 is Disk changed, DS0 is assumed and the spindle
speed is 360 RPM.

You can get them readily in black or white faceplates or even
faceplate-less.

FWIW,
Chuck