Subject: HP 9121

From: "Davison, Lee" <[email-masked]>
Date: Tue Jun 10 10:55:45 2003

While dumpster diving at the end of a radio rally (what,
doesn't everyone do this?) I found, in with the usual PC
scrap, an HP 9121 dual disk unit.

The unit powers and a small LED flashes five times but
that's as far as I've got because I've not got anything
to plug it into.

I take it I can use DSDD 3.5" disks in this and that with a
General Instrument HPIB card and some hand rolled code I can
try it out. Anyone done this? Any pointers to where to start?
Any online docs for the command set/protocols?

Cheers,
	Lee.

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From: [email-masked] (Tony Duell)
Date: Wed Jun 11 22:26:22 2003

> scrap, an HP 9121 dual disk unit.

Right...

> I take it I can use DSDD 3.5" disks in this and that with a

Yes. IIRC. the 9121 is actually a single-sided unit (the 9122 and 9123 
being the double-sided versions), but obviously you can use DD disks in 
it. It is double density, but not high denisty.

> Any online docs for the command set/protocols?

It's going to be either SS/80 or Amigo protocol (I forget which). And 
I've never found docs one either on-line (I have some printed 
documentation from HP on this, which I guard with my life -- it's that 
hard to find!).

-tony

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From: Bryan Blackburn <[email-masked]>
Date: Wed Jun 11 22:27:06 2003

These drives are notorious for having broken mounts at the heads. (Best 
to open it up and check before popping in a disk) Sometimes they can be 
fixed, sometimes not. Often the magnet wires must be resoldered. I 
bought six of the dual disk models at surplus and managed to find only 
two repairable drives out of all.

-Bryan

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From: Joe <[email-masked]>
Date: Wed Jun 11 22:36:00 2003

I missed the first part of this thread but if you're talking about HP
9121 disk drives then you must be kidding. I've used plenty of these drives
and I've never found one with a damaged head. The 9121 is VERY reliable. I
wish I could say the same for the HP 9122! (And all the other HP drives
that use the same bare drive such as the 9153, 9133  and HP IPC). I've seen
plenty of them with deamaged heads due to the mechanism not lifting all the
way and the top head hitting the disk cartridge.

   BTW I've bought loads of these surplus and I don't think I've ever found
a bad one.

     Joe

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From: [email-masked] (Tony Duell)
Date: Wed Jun 11 22:39:30 2003

> These drives are notorious for having broken mounts at the heads. (Best 

No. The _double sided_ drives, used in just about every other HP drive 
unit of the time, are notorious for having the top head ripped off. The 
grease on the eject linkages goes hard, the eject mechanism doesn't latch 
up correctly, and the top head is ripped off by the disk as it ejects.

The 9121 has single-sided drives, and doesn't have this problem.

-tony