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Replacement drives for a HP 9121D & 9122D

Tony Goodhew
 

Hi all,

I just acquired some 9121D & 9122D's and the drives are all failed. Some of them have the classic 'head ripped off' issue, some just appeared gunked up. I haven't yet had any luck cleaning those out but I'm still trying.

I'm wondering though if there is a modern replacement drive (or even NOS old drives) available out there that I can't seem to find.

Any recommendations/suggestions?

Thanks,

TonyG

Jack Rubin
 

I really like the 9122 drives in terms of reliability (of both drives and media). I've had excellent luck restoring them - I've been through a half-dozen or so and all except one have been fine once the drives are freed up (the only failure had obviously been flooded and the drives were corroded and rusty).

I use spray contact cleaner to dissolve and then flush out the old lube. The most gummed-up part is usually the large flat plate on the right side of the drive (viewed from the front). It's just a matter of applying solvent, letting things sit for a little while and then starting to wiggle things as they loosen. As long as you're patient and don't force anything, I expect you'll be successful. There is probably no need to apply lubrication after cleaning since (1) there is probably a little residual lube and (2) you're unlikely to subject the drive to heavy use once you've restored it. If you do want to lubricate the moving parts, I'd consider a minimal amount of Nye synthetic clock oil.

I also very carefully clean the heads with alcohol on a swab while the drive is removed from the chassis. If you have problems with a single drive, you can also swap their positions - I think there is a small switch on the back of the drive to set it for 0 or 1;  my memory isn't clear on this, so check the manual.


Jack

 

Paul Berger
 



On 2018-08-17 4:54 PM, Tony Goodhew wrote:
Hi all,

I just acquired some 9121D & 9122D's and the drives are all failed. Some of them have the classic 'head ripped off' issue, some just appeared gunked up. I haven't yet had any luck cleaning those out but I'm still trying.

I'm wondering though if there is a modern replacement drive (or even NOS old drives) available out there that I can't seem to find.

Any recommendations/suggestions?

Thanks,

TonyG
_._,_._,_


The first big hurdle is the fact that HP used drives that rotated at 600rpm instead of the more common 300 rpm.  For the single sided 9121 it is likely the only place you will get a replacement is from another 9121.  For the 9122 S&D models there where two versions of drives.  The early 9122 used a full height drive similar to the 9121 drive and again for a replacement the easiest route would be to get a drive from another 9122.  The later version of the 9122 used a half high drive that HP also used in a lot of other equipment so they are easier to find.

It is possible to use one of the half high 720K drives to replace a full high, but there are a couple problems.  The first is the pinout of the drive connector is different so you need to remap the pins.  The second problem is a half high drive that replaces a full high will run on a extra long time after  the motor signal is dropped.  It seems that the half high drive has a motor off delay built into it and the full high does not, so the controller for the full high keeps the motor signal active longer than the one for the half high.  I have not tested this theory, this is based on my observations when I adapted a half high into a 9133 the motor seemed to run on for an extra long time, later when I replaced it with the full high drive it was designed for, the motor stopped after a more reasonable time period.

None of these problems are insurmountable  300rpm drive could be used but it would require at least altering the clocking of the floppy controller chip, but could also require changes to the units control code.   The long run on with a half high replacing a full high would likely require code changes.  I only 9122Ds that have the full high drives so I have not had an opportunity to compare the control code.  The two version of 9122 S&D have different controller boards likely to accommodate the difference in connections.  

There is also a 9122C model which uses 1.44MB diskette drives and they are very close to "industry standard" half high drives and I have successfully replaced them with drives from a PC, but not all will work because some drives and especially later drives do not have the signals available that the HP unit looks for especially the "ready" signal.

Paul.

Tony Goodhew
 

Just wanted to thank the group for their help – I got the 9121 working following the suggestions and now I’m starting on the 9122.

 

Thanks for the help again,

 

TonyG

 

Sent from Mail for Windows 10

 

Mark Bielman
 

Good job Tony! I have worked on these as well but mine have drive issues and parts are hard to find, sadly.
(that actually might be my 9122 - I have way too much HP gear)

Mark

Mark Bielman
 

by "drive issues" I mean the motor drive/tach circuits
(bad Hall effect sensors, I think)