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HP9114 repairs (not for the faint hearted)

Posted by Steve (Australia) on 9 Sept 2000, 12:40 p.m.

9114 Repair Hints

This was a response to a question about problems with an HP9114 disc drive. Maybe this could be useful to someone sometime...

Oh, and by the way, the originally reported fault was that the HP41 reported TRANSMIT ERR when tryind to get the HP9114 to do anything, so read this with that in mind.

But first a message from our sponsor

If you're not familiar with the 9114, then you may be interested in some of the commands that you can use to make it do the basic sort of stuff.

To load a program: READP (filename in alpha)

To save a program: WRTP (note program name in alpha, optionally followed by a comma then the filename (defaults to program name))

To list contents of disk: DIR

To format a new disk: NEWM (prompts for directory size I use 50 when I'm testing)

To delete a program: PURGE (filename in alpha)

Also READA and WRTA to read and write all, READK and WRTK to read and write key assignments, and many others :-)

If you have an HP-IL interface check its quick reference or manual

Back to the problem

I'm assuming that there's no warning lights...

Then (in order of decending probabilities):

1) you have a fault in the HP-IL interface of the drive
2) the battery level is way too low for the drive to work
3) the drive is not turned on
4) one of your HP-IL cables just broke
5) the HP-IL connectors on the drive are somehow faulty
6) you just developed a fault in your HP-IL interface
7) you are misreading 0.0000 as TRANSMIT ERR :-)

Assuming that you know how to turn on the unit, then 1 is the most likely, 2 is a possibility, 3 means it's time to slap yourself around a bit, 4 is just silly (assuming you've tested your HP-IL interface on the cassette drive), 5 is a rather remote possibility (I'd put it behind a cable break), 6 is well, i've never actually seen a broken HP-IL interface, and 7 is... umm... a joke :-)

You've got to understand that it's early in the morning here, and I say some silly things when I've just gotten up.

Back to sensibility...

Are you familiar with the start up self test these drives do?

A discussion of the self test

For this unit, turning it on will result in 2 red lights (power and fault) for a few seconds, then the fault light goes out and all is well. If you start it with a disk in it, then the drive does a read/write(?) test on the disk and the whole test takes a bit longer. Likewise, the fault light goes out, leaving the power light on.

Note that the newer 9114B has more lights, and since I don't have mine here to look at, I can't confirm the exact sequence for it.

General fault-finding stuff

Do you have the unit with 2 lights, or 4 (or was that 5)?

Have you replaced the battery? (Or confirmed it it OK) Note that this unit WILL NOT run from the charger alone.

If you turn it on with a disk in it, the drive will do a self test. If this results in the fault light going out, then the drive thinks it's OK.

The drive with 2 lights has no low battery indicator (can anyone confirm this?). The newer version with more lights has them set up as a fuel guage, i.e. more lights means more charge available. For testing, make sure that they're ALL on, otherwise the drive may decide to stop doing certain things (i.e. writing to the disk).

The internal battery is a SLA battery. It's easy to replace, but if there's problems with your drive, then maybe you don't want to go for that expense. If you're a bit handy with things, then you probably could replace it (temporarily) with 4 nicads of whatever size will fit. Don't expect the charger in the battery pack to work correctly with them though.

Openning up the unit requires a #8 TORX screwdriver. They're the ones that look like an allen key except they have scalloped faces (concave). The screws are so far down little thin holes that you really need a screwdriver. I took my drive under my arm to an electronics store and tried all the TORX drivers until I found one that was the right size and long and thin enough.

Once you take the bottom off (remove the battery first) you'll see the drive and a single large PCB. You'll also see the HPIL connectors and where they conect into the board. Maybe the connectors have become lose or something (I can't see that's likely unless someone's been there before you).

Even if the dive does not work, then there are parts that are valuable in getting another drive to work. At the very least the drive itself (the drives are different between the A and B versions) and the battery pack (some seem to be missing this) are items that you can swap to other units.

The drives are so big and chunkey that you can actually repair them! I removed and reattached the head of one (in a 9114A) because it had become bent out of shape (well the suspension for the head had). If you think it's fiddly to put a card reader back together, then a disk drive is even worse. There's springs in there that work against you.

Oh, check that your drive has heads! The common fault of these drives is that the lubricant hardens and the eject mechanism slows down. After a point, the eject must be completed manually (i.e. you have to pull the disk out) If this is the case, then it is quite possible that the heads are not out of the way, and the disk shutter will tear them off (or in my case just bend them way out of shape). If pushing the eject button (without a disk in the drive) just makes something in the drive go up and down, and it doesn't latch, then your drive has it BAD and may have head damage.

Fixing eject problems

(Check out the next section for a blow by blow description of openeing the drive up)

This too is easy to fix if you catch it early. Take out the drive (the earth lead can be a pain to remove, and you will probably have to move the the main board (just a little) to get the screws back in (same as the ones that hold the cover on). Then take off the cover off the 3 1/2 inch drive. 1 screw does this on both types I think?? Or maybe one clips off. Then you'll be able to see the levers and things that make the eject mechanism work. They are all down one side of the drive.

Now get a cotton swab or something and using alcohol, or degreaser or something that will act as a solvent for the grease, wipe away the old hard grease. remember that it's behind things too, so work the eject mechanism, and get the grease out from behind everything you can. At some point the eject mechanism will start to work again. If it hasn't been latching, the first indication is when a small lever jumps up and locks the drive in the eject position. This is a good thing, but it does not mean you've got all the gunk out. The eject should be snappy. When it is, put the drive down and come back tomorrow.

The drive will no longer work! The solvent had softened some of the grease, and heat had done it's part too. So start again, and get the drive working again. (Then again, maybe you're lucky (or thorough) and did a good job the first time)

Keep repeating this until the drive works the next day, or you get sick of it.

Now use a light machine oil to LIGHTLY lubricate the parts that obviously move against one another and work the drive to make sure the oil gets to where it's needed.

Then put it all back together.

OK, I'll admit it. After I get the thing ejecting again I put it back together to make sure everything still works, but sure as eggs, it's gummed up again the next day, so I go back through the routine again until I've done it properly.

I've used this technique on about 10 drives of this vintage, and assuming there was no head damage, have had 100% success. I've only had one drive with head damage that was recoverable. In hindsight, the only reason why I attempted the fix this one, rather than earlier ones is that when I first did this there were quite a lot of drives (the 3 1/2 drives, not the 9114 units) around, and binning one was not such a bad thing.

Repairing a damaged head

Note that this applies to the drive in the 9114A. The drive in the 9114B is different and does not seem to suffer from the lubricant problem (so far) and thus does not have the broken head probelm.

First open the 9114. Then remove the drive (the big silver thing DUH!). Use the #8 TORX driver to remove the 4 screws holding the aluminium plate the drive is on. Remove the two connectors, and the earthing strap.

Then you'll find the plate is helt on by 4 philips screws (why not TORX?) Don't bother to remove this yet.

There's one funny screw at the bacl of the drive, but a normal screwdriver will remove it. Take this off. then the shielding from the drive.

Oh, and check out the model Number. It's a SONY Model OA-D43W-11. For some real fun, try locating a new one of these :-)

If you look at the side opposite the serial number then you'll see a number of levers and springs that do an awful lot to eject the disk. If you're reading this section before cleaning and lubricating the drive, then this is what you have to clean.

If you're going to repair the head, then clean this first, or you'll be repairing the head again real soon...

In any case, insert a disk and eject it a few times to see how it works.

In brief, head is up. disk slides in, and shutter is opened. disk goes in a little firther and a lever is moves into a slot allowing the heads to drop and preventing the disk from being forced out. The movement of this lever also allows another slider to move back, droppint the disk into the drive.

Pressing eject does the reverse. eject lver pushed slider whech lifts disk. lever drops into slot lifting heads and freeing the other slider which forces the disk out. On the way out the shitter closes.

With the gunky lube problem the movement of the lever that lifts and lowers the heads is inhibited. It tends to stay in the head down position. Thus the disk can't eject, and when the user pulld the disk out by hand, the head catches on the front of the disk and bends it (if you're lucky) or tears it off (if you're not).

Here is a procedure to fix a bent head.

First fix the gunky lube problem (did I mention this?)

Then check to make sure that the head isn't really OK. It may rest at a bit of an angle, but as long as it's flat on the disk when it's down then that's OK.

Assuming it's not OK

The first (and easiest) thing to do is to is to fix the head.

You can see that ther are 4 small phillips screws holding the head mechanism onto the drive. If you look carefully you'll also notice a spring under and between the two closest to the front of the drive. Take a long hard look at that spring and the way it's connected to things. As soon as you remove those 2 screws that spring will snap back inside the drive and you'll have a _really_ hard time getting it back.

You should also make some notes as to where the head sits, because you're going to _really_ stuff up the head alignment too!

OK, remove the base plate (you'll need to get at that side of the drive to get the bits that are about to fall out :-)

Now remove the 2 front screws. I'm not sure whether it's better to do this with a disk in or not. I did it with the disk out. BANG! spring snaps back, small piece of metal falls out, head is loose.

Now remove the back pair of screws. This is not so dramatic.

Now you can carefully left the head back and turn it over. Then, if nothing is broken you can try to prod it back into shape. Be really careful. There's some fine wires and the head suspension is very delicate.

That's the easy part!

Now the moderately difficult part.

Fold the head assembly back and figure out how to place the back screws on again. Fiddly, but not hard.

Then figure out how to get the front 2 screws back. It's wuate entertaining, but I won't spoil it by telling you how many times you will utter rude words while you try.

Then the hard bit. You've got to get that bloody spring back on! OK, this was the hardest bit, but this is a good way to do it.

1) get some dental floss (this is really strong, you could try cotton, but then I would recommend floss, because you really should floss!).
2) hold both ends of the floss to form a loop, hang the spring on the loop. Now loop a few turns around the spring so it's less likely to fall off. DONT tie it on.
3) turn the drive over and lower the spring into the drive through a hole just next to where the spring has to go.
4) somehow snag the spring onto the hook on the head assembly.
5) keeping tension on the spring with the floss, stretch the spring back and hook it onto the other hook.
6) let go of one end of the floss and carefully pull it out.

You may like to losten the screws slightly and try to put the head into similar alignment to what it had before. (good luck). Actually if you have a disk recorded on another drive (or one recorded previously on this one) then you stand some chance of getting passabe alignment by trial and error, but you parience may need to be infinite!

Put the cover back on, and the base place, replace the drive and test it.

With any luck it now works again!

Mine did!


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