Double sided floppies for 9114...


I just got a 9114A drive and after I had a new battery pack built (with 3x2V cells), it looks like at least the 41CX is talking to it. However, it looks like the drive can only read double-sided floppies, not high density ones. I don't have a manual, so if someone can confirm this, it would be great.

I have one old disc that looks broken. I cannot format it with my PC & lifutils, and when I do a "newm" from the 41, I eventually get a "MEDM ERR".

So where can I still get regular (not high density) floppy drives?

Also, if someone has a link to the manual that would be much appreciated.



I hope people in here will not blame me for that, but I know what to do... What the h..., why not?

The high density 3 1/2' disks have two holes: one that you can open so its contents are protectec, and the other that signs if th disk is single or double density.

I have a 9114B and I use original single disks (DS SD) to record HP41 data, but I have already tested this: Just find a way to close the high-density hole, the one that is normally open when the disk is double density (it does not have an interlock, so you should use some sort of tape to lock it in both surfaces). You should take a lot of care so the tape will not be loosen and fall inside the tape driver. Use the best tape (not transparent) you have and check for its corners.

Then you use LIFUTIL, check for the options:

Disk type:  3 1/2' Double Sided
Sector size: 256 bytes (disk capacity: 616 KB)
Interleave: 2 (I always choose this, because it's default)
Directory size: 440 files (I always choose 440, because I think I'll never have neither so much files nor so big ones)
If everything is fine, the disk space is automatically set to 616KBytes. This way, the disk will be ready to accept 130 KBytes of data (about 50 HP41CV fully loaded). If you have an HP82183A Extended I/O Module, you can load a program that's listed in the manual and use the full 610 KBytes, about 250 HP41CV fully loaded, no X-Memory in account. The problem is that the program does not run without the Extended I/O and it uses about 890 butes of regular memory.

If you need more info, post again.

Hope this helps.


Thanks for the reply! Got a disc formatted with lifutils. Had no luck writing to the disc yet :-(. I get "TRANSMIT ERR". Busy charging the battery to see if that will work.

Is the eject button supposed to latch in the "in" position with no disc? The drive will happily eject discs, but the eject button always comes out all the way, with or without a disc.


Hi, Daniel;

I'm glad you could format the disk. Unfortunately, my unit is a 9114B and it seems to me the drivers for the 9114A and 9114B are different. The fact the eject button is all the way out even without a disk may be normal in the 9114A driver, I don't know.

After charging the battery, keep in mind the 9114A Owner's Manual (mine is a hardcopy of the one that comes with the MoHP CD Pack; valuable pack; anyone dealing with HP calculators should have it) recommends using the unit with the charger always connected. I had in mind that rechargeable batteries should discharge (not completely) from times to times, but I changed this procedure when using the 9114B: AC charger plugged in all the time.



Uau ! Last time I heard of it was in the 80's, when we used to puch holes in the diskette magazine as for it "look" like high density diskettes for a PC computer. Tricks are allways the same !


E aí, José? (What's up, José?)

You're right! Sometimes I feel I'm in a DeLorean and getting back in time... straight to the past. Or, at the time we used our HP calculators for the first time, it was definitely a glimpse... of the future we're living now.

What a bunch of silliness I wrote here...



Thanks for the reply. I will have to get the CD. According to the battery guy, lead-acid batteries are the complete opposite of NiCads (which need to be discharged completed to avoid the "memory effect"). Discharging a lead-acid battery completely is bad for it, so it is better to have it topped off.


Hello Daniel,

Though I haven't got a 9114A/B yet, I have several 3 1/2" Single Density Double Sided disks (don't pannic!! I'm not willing to sell you nothing.) If you want to make a try with some of'em, please e-mail me with your mail address and I'll be glad to send you some (as much as I can fit into a regular size envelope for card weigthed post fare, so I think that I can send you 4 or 5 at least.)

The disks are obviously non defect, 720KBytes standard PC formatted and have no data.

Hope this helps you to check the 9114 functionality.

Best regards from the Canaries!!


1) Search the archives for 9114 articles. Check also the
article on 9114 maitenance.

2) Clean the drive and the head in particular. 9114A drives are likely to have problems with the eject mechanism (although the eject button stays out even if a floppy is not in the drive). If the eject mechanism is sticking, you are likely to damage the R/W head (if its not already damaged).

3) Apply Viera's fix on a normal floppy (with the provisos mentioned in the articles above) and try to format a diskette. If it fails with a medium error, your drive is probably damaged and you need to go back to step one.



Thanks for the reply. I have seen the article on 9114 repair, but that would be after I had tried all the other avenues :-)

So are you confirming that the eject button does stick out all the way, even if a disc is not in the drive?

The eject mechanism with a floppy seem to be fine - the floppy ejects quite snappily. It does not physically eject the disc all the way out the drive. It seems to have more-or-less the same action as my PC floppy, maybe a little less "forcefully". I have nothing to compare it with.

I will continue to search and tinker... Any and all tips & tricks appreciated.



I cannot answer your question about the eject mechanism on the 9114A, as I have the 9114B. On the 9114B, the eject button stays in after the disk is ejected. If your disk clicks into position when inserted, and is ejected OK by the button, it sounds to me as if the mechanism is OK -- but, alas, this is only conjecture on my part.

One of my 9114B's developed a problem with its eject mechanism, so that the disk did not click into position when inserted. I followed the directions of the repair article (Steve's, Australia) and found the repair much easier than might be concluded from the article. I did not need to take springs, etc., off the drive, but merely gave the moving parts a little WD-40 oiling. In my case the offending piece was the thin, rotating lever on top of the drive, which had become gummed up. The whole thing now works beautifully again. The only unusual tool needed is a #8 torx screwdriver to get the cabinet open and the drive removed.

I am not suggesting that you open your unit up, because your eject mechanism is very likely OK. I just wanted to reassure you that if "surgery" becomes needed, it is not as daunting as it may sound.

Good luck with it!



Thanks for the post. I did repair a gummed up wheel on a card reader without too much trouble. I will try a few more things and then its off to find a Torx screwdriver. I doubt that my driver & bits will fit the small hole.


I have both the A and B. I've had no problems with the B's. The A I have definitely had the gummy ejection problem which was fixable. However, it did have a head problem. The head had come completely off and was not repairable, at least for mine. You could remove the cover and probably take a peek at the head and determine if it appears somewhat in place.


P.S. The perfect #8 torx screwdriver is available at Sears for $2.99 -- at least it is in Maine. And believe it or not, it is made in the USA. (Sometimes I think we don't know how to make anything anymore in the USA, not even shoes in Maine.)


You wrote "I followed the directions of the repair article (Steve's, Australia) and found the repair much easier than might be concluded from the article. I did not need to take springs, etc., off the drive,..."

The surgury mentioned is what I did to repair a bent head "suspension" assembly. I'd hope that people fix their drives before it comes to that.

Actually, on that point... If you ever find a disk "stuck" in one of these drives (often because the disk shutter is fouling the head) the safest solution is as follows:

1) reinsert the disk

2) press the eject button, but hold the disk in (it's probably not going to even partially eject anyway)

3) slide a piece of paper on top of the disk so it slips between the head and the disk

4) carefully withdraw the disk

5) remove the paper

6) fix the drive!!!

You also wrote "...but merely gave the moving parts a little WD-40 oiling."

I guess it depends on the degree of stickyness :-) alledgedly WD40 will eventually turn to glue, so you may have to repeat the fix. I say alledgedly, because it's not happened to me...

You also wrote "In my case the offending piece was the thin, rotating lever on top of the drive, which had become gummed up. The whole thing now works beautifully again."

It may be interesting for you to document that in the articles section. I've not had the B version gum up, so my article doesn't mention them. If you've had the problem, then others may too. Let them gain from your experience.



I want to know if there is a way to replace the entire driver unit in case there is no way to repair it, say, the electronics + IL are fine. Is the 9114A/B 3 1/2' driver unit electricaly compatible with available, existing commercial drivers? I did not open my 9114B (yet, God bless), but I'll do it if needed. In this case, should we try a transplantation?

Have anyone thought about this? Or tried?



Vieira, Luiz C. (Brazil) wrote:
> Is the 9114A/B 3 1/2' driver unit electricaly compatible
> with available, existing commercial drivers?

If by electrically you mean the the interface has TTL levels then the answer is yes (unlike, for example, the HP-85 bus which uses 6V logic).

Unfortunately it goes down from there. On the 9114A the connector itself is different from the "standard" PC floppy connector (fewer pins), so at least you get a big hint that there are compatibility issues. On the 9114B the connector is the same as that of a PC floppy drive.

However the pin-out is different!

The 9114B is powering the floppy drive via the flat ribbon cable (while the PC floppy drives have separate power connectors).

The drives themselves are also different (they use different rotational speed for the floppy, so the interface is also very different).

So don't even think about swapping the floppy drive inside an 9114 with a PC floppy drive.

There are, available on eBay other HP equipment of the same era as the 9114, and these use the same type of floppy drives. E.g. the 9122 HP-IB comes with one or two floppy drives that are fully compatible with the 9114B.

Sorry for the bad news.




I've been wondering about the rotating speed. Would it be related to transfer rate? I have seen different standard PC floppies with different rotating speed; slightly different speed, enough we could notice by looking and measuring the time each drive would read and write the same file in the same computer.

Oh, yes; I should also consider Logic compatibility among electrical compatibility. I saw many portable floppy-drivers, and each of them has its own flex connector with different size, shape and (?) # of conductors. I have never found the time to check if they could be interchanged with each other, but the basic PC floppy controller is a standard for the PC's, right? But in the portable world, same electrical characteristics and standard do not necessarily mean same circuitry or wiring. Except for their Hard Disks, that also use the flat cable to power them.

I'd like to understand if the drivers are really 9114B dedicated units or if their transfer rate was reduced so it could be used with its electronics.

Would HP use a different drive for the 9114A/B? How different are they? Based on Vassilis' answer, I believe they have, indeed, used an specific assy.

I do not dare thinking of this event, but I'll try to collect as much data about the 9114A/B driver unit as I can, because I have a few unrepairable standard PC floppies and I'd like not to retire my 9114A/B because the driver unit no longer works. If we can format a LIF disk in a PC-like computer and later use it in the 9114A/B, I imagine transfer rate is the cause for a different rotating speed. In this case, a faster driver would be useless, of course.

Did anyone try something closer to this? Just in case we do not have original 914A/B drivers to replace.

Thank you, Vassilis; as always, your posts (as many others' posts) are full of good and concise information.



> There are, available on eBay other HP equipment of the 
> same era as the 9114, and these use the same type of
> floppy drives. E.g. the 9122 HP-IB comes with one or two
> floppy drives that are fully compatible with the 9114B.

You can also get replacements for the 9114A drive, which was the same one used in the early dual floppy and floppy/HDD units for the HP150. This is where I got my experience maintaining them.

Unfortunately I can no longer remember the part numbers, and I seem to remember that in at least one case the part number did not change (it could be the 9122, but then the early version could have been 9121...)

Not good information, but I'm sure they're out there. At one stage I could have given away dozens of them :-(

In actual fact, I did :-( :-(


Steve (Australia) wrote:

> Unfortunately I can no longer remember the part numbers,
> and I seem to remember that in at least one case the
> part number did not change (it could be the 9122, but
> then the early version could have been 9121...)

No the 9121 are single sided. The drives externally look the same as the 9114A, but they only have one head.

But if you come across an 9121, don't throw it away, its usable with the series 80 machines (HP-83, HP-85, HP-86 and HP-87). Unfortunately these machines cannot use the higher capacity drives (like the 9122) because HP changed the communications protocol that runs over HP-IB.



Vassilis Prevelakis wrote:

> No the 9121 are single sided. The drives externally look
> the same as the 9114A, but they only have one head.

The 9114A/B is single sided too. :-)


The signals on the interfaces of both the 9114A and 9114B drive mechanisms are similar to those on the PC drive interface, and are at TTL levels.
However, fitting a PC floppy drive mechanism is not just a matter of making up an adapter cable. The problem is that the 9114 drives (both versions) have sprindle motors that rotate at 600rpm (twice the PC drive speed of 300 rpm). Since the data density is the same on the 9114 disk and a PC 720K disk, this means the data rate is doubled, too.
I suppose you _could_ modify the controller board in a 9114 to work witha normal PC drive, but it wouldn't be trivial.
However, the original drives can be repaired fairly easily (this seems to be an alien concept these days!). I've rpelaced heads, rebuilt spindle motors, and so on.
In the case of the 9114B, many of the drive components (head carriage, stepper motor, many chassis parts, motor drive ICs, analogue ASIC, etc) are the same as in an Apple 800K drive, which is therefore a good source of spares.
In the case of the 9114A, many of the chips are standard parts. I had one with a faulty spindle motor (didn't turn at all), and I found that the driver chip was also used in some VCRs, and was therefore avaialble fairly easily.
Getting heads for the 9114A is harder -- I think I found a similar drive (probably from an Apricot computer) with electronic problems, and removed the head assembly from that. Aligning it wasn't hard -- although I did have to buy a 3.5" alignment disk (which was not cheap). It was just a matter of stepping the head to the correct track (as I said, the signals are sufficiently close to standard that a normal drive exerciser will work with an adapter cable), connecting a 'scope to the head preamplifier testpoints and adjusting for the right catseye pattern.
Let me know if you want to try anything like this -- I've got notes of what all the Testpoints do, and how to set up the trimmers on the controller board, etc.


Tony Duell wrote:

"Aligning it wasn't hard" ...
"Let me know if you want to try anything like this -- I've got notes of what all the Testpoints do, and how to set up the trimmers on the controller board, etc.

I, for one, would like to have this information on hand, as I expect I will need it some day. Can you share this info with little effort, such as scanning your notes, or something like that?




Alas I have no scanner (and no suitable machine to connect it to). But I will try to type up an understandable version of the notes sometime.
In the meantime, here's roughly how to align the trimmers on the controller board. You'll need the WD2793 data sheet becuase the procedure is _exactly_ as described in there -- HP made things easy for us.
What you do is remove the controller board and put it on yuo bench component-side up. Power it up -- I normally use the switch wiring harness for this (pluged into J2 on the controller) with a 6V bench supply connected between the white (ground) wire and the White/Red wire (+ve).
Then pull the '3060' jumper, which should stop the darn thing powering down while you're working on it. Move the jumper near the 2793 chip from the 'N' position to the 'Adj' position (this puts the 2793 into setup mode, and must be done _after_ powering up the board).
Connect a 'scope or frequency counder to TP3 ('VCO'). Adjust C15 to set up the free-running read clock frequency. Connect the 'scope to TP2 ('RPW') and adjust R10 to set the read pulse window width. Connect the 'scope to TP1 ('WPW') and adjust R11 for the correct write precompensation delay -- this one is not too critical.
As regards aligning the heads in the 9114A drive mechanism, it goes like all drive alignments. Connect the drive to an exerciser (or kludge one up using a PC and parallel port ...), the connect a differential-input 'scope to TP101 and TP102 on the drive logic board on FC9 PCBs or a normal 'scope to pin 1 of CN107 on FC16 PCBs.
Pop in the alignment disk, step the head to the right track, and observe the catseye pattern. If one lobe is larger than the other, loosen the stepper motor mouting screws and rotate the stepper motor to align the head.


Thanks Tony!

I had trouble finding a WD2793 datasheet on the web. It looks like the TMS2793 and SAB2793 are direct substitutes, and indeed my 9114B contains a TMS2793.

I found a TMS279x datasheet at:

From this, and looking at my 9114B which seems ok, I conclude (Tony, please correct me if I'm wrong):

  • TP3 (VCO) should be adjusted to 500 KHz
  • TP2 (RPW) should be adjusted to 250 ns (high)
  • TP1 (WPW) should be adjusted to 125 ns (high)
Interesting that these match the 8" disk specs rather than the 5.25" specs in the datasheet. I presume this is due to 600 RPM of the drive speed rather than the usual 300 RPM for a 3.5" drive(?).

I see there is a 4 pole dipswitch, normally all off/open. Any useful functions there?



I believe those settings are correct -- certainly 'VCO' should be 500kHz. And yes, the data rate is the same as that of an 8" drive. This is twice the rate of a normal double-density 3.5" drive, but then the HP one has twice the spindle speed. So it
all makes sense in the end. It's odd that HP claim these adjustments can't be done in the field, when in fact they're _trivial_ to do using quite simple equipment.
As fro the DIP switch. It selects one of 8 self-tests (the last swtich (marked '1' on the switch) sends an NMI to the processor to start a service test. On the 9114A, BTW, there are 3 links to select the test and another marked 'Start SVC' to generate the NMI.
I have a list of the tests, but no real info on them :
0 : Power on Reset ; 1 : ROM/RAM/FDC/PIA test ; 2 : HPIL test (loop back HPIL port) ; 3 : Read/Write test (-A), Reset (-B) ;
4 : Verify test (read all sectors) ; 5 : Track 0 test ; 6 : Motor speed test ; 7 : Format ;


Hi Steve,

Thanks a million for the further information, and especially for your original article. Without your article my 9114B would still lie useless in the closet. I did the repair only a week or so ago, and had meant to write to thank you -- so please let this be my THANKS.

And my apologies if my words sounded in any way critical, which they were not meant to be. I am one of those who makes a mess of most any repair I try to do, and so I tend to be fearful of anything that sounds complicated. But I was desperate to have my disk drive working again, and your description was so clear and detailed that I made a special trip to the store for the #8 torx screwdriver you told us about and gave it a try. I could hardly believe the good results.

My reading of your article was too hurried. I did not quite understand the difference between the preventative medicine, so to speak, and the "surgery" for the damaged head. Thanks for pointing that out.

I keep checking to see that the WD-40 is still doing its thing, expecting to have to go in again. But so far (which is only a few days) it is working beautifully.

Thanks for writing. It is good to know you are still there!

With gratitude, and greetings from the other side of the world,



One should NEVER use WD40 as a lubricant. It is actually a wax and will eventually gunk up again... bad... really bad.


Hmm....I don't know, David. Have you had bad experiences with it? I have a couple of Westclox Baby Ben's from the 1950's that stopped running long ago, until six years ago I sprayed them with WD-40, and they have been ticking happily ever since -- although one of them did once need a second dose. I'm sure that my behavior would cause a clock maker to lose his dinner, but these old five dollar clocks are now keeping good time just the same.



what I have noticed is that WD40 sometimes may act as a solvent for some sort of ink. It also goes inflates some rubber-based material.

Anyway, I use it as lubricating material without any trouble. I avoid flexible plastics, but its a particular option.

My US$ 0,05.


WD40 is not a lubricant, agreed. It _will_ turn to a waxy substance, which will lock most small mechanisms totally solid!
I've had far too many things cross my bench which have been sprayed with WD40 and are now in a terrible state. The only thing to do when this occurs is to totally dismantle the unit, soak the individual parts in solvent, clean them, re-lubricate with the right oil, and then reassemble.
I have an (totally mechanical) camera here that I got cheap because it wasn't working. The real fault was one spring had come unhooked in the slow speed escapement. Repair : Remove baseplate (7 screws), hook on the spring, put the baseplate back.
Unfortunately, the previous owner had sprayed WD40 in everywhere. Everything -- even the exposure meter movement -- will have to come apart for cleaning. A very long job.
Be warned that if something comes to me for repair and it's been spryed with WD40, then the repair charge is multiplied by 3 (at least) to cover the extra time in removing said substance.
It's for this reason that I can WD40 (officially 'Water Displacement formula 40') 'Wanton Destruction 40'. It really makes a mess of things.

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