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

Paul Berger phb.hfx at gmail.com
Fri Nov 24 10:22:24 CST 2017

On 2017-11-24 2:02 AM, Chuck Guzis via cctalk wrote:
> 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.
> Chuck
My old Compaq system has one of these drives in it so I pulled out out 
to take a look and yes it should work however the signal cable connector 
is on the left looking at the back which is the opposite of where it is 
on the Sony and YE Data drives.  The signal cable inside the 9122C is 
pretty tightly folded and it would require modification if you wanted to 
put the drive in the right bay but should be ok in the left one.

I also got a Panasonic JU-257A606P to work once I noticed the head 
stepper was unplugged.  This drive apparently has versions with switches 
on the board to change the configuration.  The drive I have does not 
have these switches but wire jumpers on the pad work just as well.  This 
drive also has the signal connector on the left.

Forgot to mention that the 9122C uses select 0 for the first drive 
normally the left one,   and select 3 for the second drive.  Most newer 
drives do not have a provision for using select 2 or 3 and indeed since 
many are aimed at the PC market they are hard wired for select 1.  I 
just remapped the select pin in my case connected pin 6 on the cable 
(select 3) to pin 12 on the drive (select 1).  Unless your drive can be 
set up for power on the signal cable like the original Sony drive, you 
will need some kind of an interposer between the cable and drive anyway, 
and it is easy to remap pins there.


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