HP 9121 Problem with disks


Hi, I have an 9121 Floppy connected on a HP86B but no disk. I have only 3,5" DD disk - how can i use this disks with the 9121 ? Are they formatted in a CP/M format ?


I have been using a drive of the same vintage with what we used to call 720K disks with no problems.

Back in the days of steam radio I was using these old HP drives and I remember the single sided media (the 9121 sounds like the SS version (blue button?)). When the double sided version came out, (9122???) HP included lots of information about which disks could be used in which machines. Basically, the double sided media was OK, and the double sided drive could read single sided media (you may find old original HP150 disks are single sided).

As to the format... I'm sure there must be a command to initialise disks. But I'm afraid I can't help you with any information about what it could be.


Hi, yes there is a command "initialize" but the HP says "disk error"...... :-(


OK, there are several things that could be wrong.

1) address of the drive

2) dead drives.

In the first case, try all the addresses unles you have a better way :-)

In the latter case, open up the unit, remove one of the drives, and tale off the cover. Check that the head(s) (9121 = 1 head) are still intact, and are not bent (problems with sticky lubricant on the drive can lead to the head being beny to completely ripped off).

If it's OK, run a head cleaning (wet type) through the drive for a while. This has resurected one drive of mine. It would get a few tracks through formatting, then give up.

Bent heads (and it's the top head on double sided drives) can be fixed bt carefully undoing parts of the drive that hold the head in place, swinging the head assembly into place, then carefully bending the head back. Then the almost impossible task of putting the drive back together starts -- it _is_ possible (just bloody difficult). You may never get the head aligned correctly again, but the drive may work. I have fixed one drive like this too.

If you've got bent heads (or the early symptoms - disks that don't eject easily) then you need to do something about the lubricant so that the problem doesn't get worse or recurr. This is just a case of carefully removing all the stivky lubricant (on only one side of the drive) and then lightly lubricating it with light oil or some similar lubricant.

Of course the eectronics could be fried too... Oh dear :-(


The INITIALIZE command syntax is as follows:

INITIALIZE "vol_label", ":msus", [directory size [,interleave factor]]

For example: to initialize the left drive in my 9121, which has hpib address of zero:


The default directory size for a 9121 is 14 records, or 112 files. You can ask for, say 256 files by specifying a directory size of 16 records (each record can hold the directory info for 8 files).


If you want to initialize the right drive, you issue


I hope this helps,



You can use "ANY" 3 1/2 Disk with your 9121. (1.44M too)
Be sure each square hole in disk are "closed"

then Type "INITIALIZE"


The disc used in the early version of the (sony made) 3,5" drives are marked "SS". they could take some 250 kbite. As far as I know, the comand for formatting is "initialize" but I will check. I still have some 50 disc's in the "SS" format and also lots of 5,25" disc's fot the 86B series.


The Floppy works, but i get the message error 130 : disk ??


from p. 384 of the hp85 manual:

Error 130: The storage medium is not initialized, the drive
door is open, or the drive number specified is not present.

Try a fresh single density (720K) floppy and initialize

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