Faulty disk drive in 9114B ?


Hi. I have been checking an old 9114B disk drive with a 71B.
The 9114B unit seems to work, but it fails when I send any command.

I have noticed that the disk drive makes the usual seek when the unit is started but does not perform any test at all when I put a disk on it. The manual claims the unit should perform a 5 seconds extra test when the disk drive is loaded with a disk. By the way, the test light is ON for a couple of seconds only, not the claimed 6 seconds.

When I send de command DEVICEID I get back the string 'HP9114B'. So it looks like the logic in the unit is working.

However, when I use the command INITIALIZE I can see the unit trying to do something but the head does not move at all. The led on the front of the disk drive is off all the time. It never lights up. If I remove the diskette and send the INITIALIZE command I get the expected 'No media' error so it seems that it is working to some extents.

I have checked that the heads are able to move up and down smoothly when the disk drive is first powered up.

I have even tried with preformated 720KB diskette. But all commands fail.

By the way, I have been using HD diskettes with the hole taped, not true DD diskettes. May this be a problem?

The unit has some dirt on it but I have seen much more dirty disk drives units working.

Any guess ?


I don't remember whether the 9114B uses a mechanical or opto switch to sense disk presence. Is your tape over the hole opaque?



I recently bought a 9114B drive and ended up removing the diskette drive to fix sticky ejecting so I remember some of the actions my unit took at power up. With the top cover of the 9114B removed, if you turn the unit off and put in a disk and then power up, does the diskette platter spin and the head move back and forth? If the floppy is not spinning and the heads aren't moving and the disk access disk is off, then I suggest you remove and re-connect the the ribbon cable connectors at the drive and on the circuit board ends just in case there is a dirty connector.

It would be interesting to hook my 9114B to my 71B, disconnect the floppy drive ribbon cable and see what the 71B reports when I try an INITIALIZE command. In the meantime, check that there aren't any broken wires around the head position motor. How clean is the diskette drive itself? Is a floppy disk hard to insert or eject from the diskette drive mechanism? I'm trying to get an idea of the condition of the drive itself.

There are a couple of good articles at this website covering 9114B repair, like #78 by Steve of Australia and #876 by PeterP. These may not cover your specific issue but it can help you get an idea of what can go wrong with the 9114.

At this point, I wouldn't worry about double verses hi-density floppies as right now you just need the drive to work. After it's working then should worry about selecting the proper media.

I'll play with mine tonight and get back to you.


Edited: 7 Dec 2009, 4:30 p.m.


At this point, I wouldn't worry about double verses hi-density floppies as right now you just need the drive to work. After it's working then should worry about selecting the proper media.

DD drives often won't recognize HD media at all, because the presence detect sensor expects the rigid shell of a disk to be present exactly where the HD sense hole is found on an HD disk.

If the drive isn't sensing the presence of the disk, it will exhibit exactly the symptoms that were described.

That's why you can't just "worry about selecting the proper media" later.


Eric, your right, I had forgotten about that. And, as I remember, the diskette presence sensor in the drive is where the double density, hi-density hole is in the floppy. So, inaki, if you only have hi-density floppies available to you, be sure to cover the right-side hole. Then see if you still get a 'no media' error when you try to initialize a diskette.

Thanks Eric for keeping me straight. Inaki, let us know how it goes.



Hi, inaki;

I have a 9114B unit (a gift) and after not being used for some time (about half a year) without charging the battery, it came up with many faults related to the disk drive itself. Battery charged OK, all 4 LED´s lit (battery charge and power), but when I tried any operation that would power the disk drive, all LED´s went down and I got some error message (cannot remember which one).

For shortening the text: it was the battery. It charged OK but had some internal problem (high internal impedance) so it could no longer maintain high current (or current peaks). Hence, with no power to activate the driver, the unit either reset or sent an error condition back to the IL controller (the HP41, in this case). This is the non-definitive battery I used at that time. Now it has a 2800mAh instead

After that, I always keep the battery charged because it is a sealed lead-acid, and the main recommendation is to keep them always at maximum charge; if discharged, charge them ASAP.


Luiz (Brazil)

Edited: 7 Dec 2009, 6:22 p.m.


Thanks for your thoughts guys!

After checking everything I checked the power by measuring the current the unit takes when in standby mode, when using logic commands without resource to disk, and finally when using commands that involve the disk.

When the 9114B is in standby mode or receiving commands that do not involve the disk it takes a small amount of current. But when the disk drive is involved the current taken raises a lot, up to 1,5A (in my measurements, but probably is higher than this).

After reading the Luiz message I decided to replace the battery with a regulable lab power supply. I started with 7.3V and 1A, just not enough to feed up the disk drive. The symptoms were exactly the ones mentioned in my first message. Then I raised the lab power supply limit to 2A.

And voila, the disk drive started to work! The initial startup test was performed as expected with the heads moving up and down. The led on the front of the disk drive was alive!.

It was the time to test commands from my 71B. Bingo! I was able to initialize the diskette!

So my guess is that Luiz put the hammer in the nail here. The battery may be good enough to feed the logic but not enough to feed the disk drive in every work, even when the 3 leds in the front show full battery.

As a side comment. If ones tries to use a power supply that bypasses the battery as I did for the tests, it must be a power supply able to raise current to about 2A (for about 7.5V). I tried to use some higer voltage, up to 9V, without problem. However it would be mandatory to check the power regulators specifications to see whether it is wise to use a higher voltage power supply.

As I could see for this case, and others related to 9114B in this forum, it seems a bad battery can cause a lot of trouble.

Thanks for your help!

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