Broken Zip drive

[The Macster]

As I said in the topic about the PowerBook Duos, I was also given two Zip drives with the bunch of Duo bits, one SCSI and one USB. The front bit of the SCSI one is loose though, and a piece of plastic inside is detached. Looking at the USB one for comparison, it looks like that bit of plastic should be attached just above (ie towards the back of the unit) the circular bit that is under the transparent window on top of the drive. It looks to be attached by a spring, which has presumably come loose in the SCSI one. I was just wondering whether it's possible to rectify this, as a SCSI Zip drive would be useful for old Macs (I already have a Parallel one, so would have the full set if this one was to work again ). I can't even see how you are supposed to go about opening it up, as I can't find any screws on the outside at all - anyone know? Thanks

 

[wally]

No screws, hidden plastic latches. [}] ]'>

There are three internal latches that are best undone with a custom made tool. Look for two access slots (.6 mm high, 13.5 mm wide) left and right, midline along the sides and 4.25 cm back from the front face. Look for one midline access slot 12.5 cm back from the front face on the left. There is a latch 17 cm back from the front face hidden just above the right midline, you will see a rectangular opening 2x4 mm into which a barb engages. If the first three latches can be freed the last one detaches by lifting the entire left side of the case top and hinging the cover clockwise.

The three latch arms arise from the base and need to be pushed inwards to free them from top cover inwards pointing barbs. It's important to push them in one at a time before lifting, because lifting first tends to lock the latch in position.

You might think that a small screwdriver, put into each access slot and pushed in firmly would do, and it might. But most screwdrivers are wedge shaped and immediately start prying the case halves apart before they even begin to bend the latch arm inwards. Better a piece of steel sheet metal .5 mm thick and as wide as will fit the slot, 4 cm or more long, with the last 7 mm bent up at 60 degrees. Stick it through the slot with the bent end upwards, lift the free end to pry the latch arm in with a degree of control not possible with a straight inwards push, then separate the case in that area. Steel tin can material is too thin, but a double length piece folded over and hammered flat might do if thicker stock is not at hand. Yes, tin snips, anvil and hammer can be a part of the computer repair toolkit. [] ]'>

 

[The Macster]

Thank you! Now that you point out where they are, I can see that someone's been inside it before as there is minor damage to the plastic casing around the first three points, where someone must have used a screwdriver that was slightly too big to release them. Maybe what they were trying to repair was this bit of plastic that seems to have become disattached. I don't know if you're familiar with the inside of these things or not, but if you are it's a three sided piece of black plastic which surrounds the rearward side of the silver disc at the front of the drive. It seems to be unattached on the right-hand side - should it just be pushed back into the track that it looks like it fits into? However, the spring that I can see inside the USB Zip drive on the left hand side of this bit of plastic is not there - presumably that is needed to make it work? Anyone know what this bit of plastic (and the spring) does? Presumably it is something essential to the operation of the drive...

 

[Charlieman]

I'm enjoying Wally and Macster's exploration of the innards of a Zip drive. And I definitely won't knock it if they fail or win to fix the drive. Which is hard stuff (win I mean).

I presume that Iomega have some calibration tools that they use to "fix" the microscopic differences between components (especially those that have been broken and reassembled). The Zip is just a fast floppy drive that uses simple fluid dynamics to lift the head from the magnetic layer. With lots of patents to protect the design.

If the disk head mechanism is broken, I find it difficult to believe that it is reairable in the field (or anywhere). If it is just the disk inject mechanism, suck it and see.

 

[wally]

...Presumably it is something essential to the operation of the drive...

Indeed! As a zip drive is inserted, that arm gets pushed back and reaches a position in the rear where it opens the sliding metal shutter on the zip media so that the read/write head assembly can access the zip disk!

At about the 9:30 position of the drive arbor that three segment arm needs to have a post of some kind into the deck to pivot upon, and just to the left of the pivot a tab for the spring to engage that pivots the arm clockwise until it reaches a travel stop at the front edge of a semicircular track where it waits for media insertion.

The spring assures that the arm is forwards enough to engage the right hand edge of the shutter. If the arm is full back when media is inserted, the arm will not catch the shutter to open it to the left, rather it will just rest on the rearwards face of the shutter.

The arm right end should indeed be muscled carefully into that semicircular track slot.

 

[The Macster]

So without the spring there's nothing that can be done? (I can't hear the spring rattling around inside, so presumably it's been lost previously)

 

[wally]

Well, if you have the two places the spring attaches to both intact and if the arm pivots correctly, you could use any weak small spring you could fit in there, including a rubber band like the orthodontists use or one that you cut from a balloon or bike inner tube. It just has to be strong enough to swing that arm forwards, and weak enough not to wear out the pivot or break off either of the attachment points. Of course, an exact replacement spring steel one would be good (and the least likely to deteriorate and/or give off contaminating particles), and the original has a 10 mm coil length contracted, 17 mm installed, coil portion extends to 21 mm when arm full to the rear, 2 mm outer diameter. Add another 2.5 mm total for the attachment point loops. If you do pop the cover there's another spring similar (but possibly shorter) to it used as the head assembly retractor, just in case you need a visual to go on. Hey, just improvise! You could be the only person in the world transferring data assisted by a spring made from a toy balloon! [] ]'>

 

[wally]

I rigged a trigger pull gauge which says 300 grams force at the spring to move arm fully to the rear. Just in case you want to apply Hooke's law and get it just right. [8D]

edited addition: You can try to test the Zip drive just to see if it otherwise works by using some transparent tape on the topside to manually secure the zip drive media shutter in the open position before you insert it. I have not tried this in a springless drive, but unless they have some sensor interlocks verifying the arm goes fully forwards it should work.

 

[The Macster]

Thanks for the excellent info I think what I might do is try to scavenge another dead/unwanted Zip drive, as it sounds like the exact spring will be the best one to use, and presumably all Zip drives (internal/external/parallel/scsi/usb/100mb/250mb etc) all have exactly the same size of spring in that position? At least I'm assuming they would...

 

[wally]

A good bet within the Zip 100 size, don't know about the higher density media drives. Likely the next good or bad freecycled Zip 100 drive will have your spring. Even better, freecycle a Zip 100 plus drive that auto-senses scsi or parallel so you can bridge between machine families with it and your USB Zip drive. [] ]'>

I'm uncertain if Zip 100 drives are a protected species like DUOs, and whether you can be shot for Zip drive dumping... [] ]'>

 

[wally]

So without the spring there's nothing that can be done? (I can't hear the spring rattling around inside, so presumably it's been lost previously)

Springs have feelings too. They lust for deep pile carpets, home heating air duct grills, and the strong embrace of the rare earth magnet that supplies the field for the head actuator. If that spring got loose when the zip drive was accidentally dropped, you might find that it is having an intimate affair with the actuator magnet. [] ]'>

 

[The Macster]

I can't see it in there (I'm assuming the big rectangular gold-coloured piece of metal is the actuator magnet), although I can't see underneath the magnet (but then again it looks like there might be some plastic between the bottom of the magnet and the circuit board anyway).

 

[wally]

Inside that gold colored rectangular area is a magnet sandwich: top gold tint steel plate, gray strong magnet glued to underside of plate, air gap where coil travels back and forth to move head, steel plate for inner magnetic field return path, other half of air gap and coil, gray strong magnet glued to bottom plate, bottom steel plate. The really strong field is in that air gap on both sides of the center steel plate, right where the coil travels. Weak field outside the sandwich. If the spring got in there it would block movement of the arm assembly. If you can see it, it can be fished out with copper wire or something non-magnetic. It would be good to assure no spring trapped before trying the tape the shutter open and try writing 100 MB test I suggested earlier, do not want internal collisions!

 

[The Macster]

I can't see the spring just from looking where you say - I presume it couldn't have got in there somewhere where I wouldn't be able to see it from the top without taking the magnet off or anything like that (assuming that is even possible)?

 

[wally]

Mine has a plastic cover around the gold part that really blocks the view and that I am reluctant to remove because of risk of misalignment. A dental mirror does not help much. I do not know how far in a spring could have gotten because the spring and the gap are so similar in size. What I did to check travel was to tape back the spring arm on the right and unlatch the left side lower coil latch with a paper clip. Then with another paper clip I advanced the head assembly gently full forwards by pushing on the plastic rider on the right hand side wire guide. With the coil and arm full forwards you can see the two heads and the REALLY tiny wires, very important not to touch these. If you get to full extension you can see what looks like the front half of a tiny integrated circuit exposed in the front cutout of the top gold plate and exactly 3 cm of arm will be exposed. There should be resistance only in the first .5 cm of travel, after that just tipping the assembly should move the arm. When you fully retract the heads they will spread at the last moment to separate then come to rest on the head rest pad.

 

[The Macster]

Right, I scavenged an internal IDE Zip100 drive from Freecycle I've popped the front of it, however can't see any way to get the top of so that I can get the little spring out - is there any way to get further inside it. I'm sure this is never going to work, there's probably something much more fundamentally wrong with the SCSI one as well, but it's worth a try I guess It would be so much easier if I could just find a SCSI one that worked in the first place (and preferably a 250 MB one as I have a parallel one of those and 6 Zip250 discs from a previous Freecycle pickup a while back), but life's never easy is it?

 

[wally]

...I'm sure this is never going to work, there's probably something much more fundamentally wrong with the SCSI one as well, but it's worth a try I guess

Heh, yee of little faith! [] ]'> [] ]'> [] ]'> [] ]'> This is how you learn!

There are four little plastic barbs along the top edges. You may be able to push the plastic side rail strip where it meets the metal turned down edge in hard with a screwdriver under each barb in turn to dislodge the barbs, or if not, you can try with a small screwdriver, or carefully with a knife blade, prying the metal top edge over each barb all along each side then lift the top off. (The spring looks the correct size to me!)

 

[The Macster]

Thanks I managed to get the top off (eventually - I'm sure you can't be meant to open these things up!) and move the spring over to the SCSI one, though if this one does actually work I will be astonished - it is probably completely dead. I can't test it for a few weeks as I'm not at home where my Macs are until then - that gives me some time to hopefully scavenge some Zip100 discs though, as the only ones I currently have are Zip250. A shame that I didn't come across a SCSI Zip250 drive, but I suppose 100 MB is enough for most vintage Mac files anyway!

Anyway, many thanks for your help May I just ask...have you worked for Iomega at some stage? Just that you seem to know absolutely everything there is to now about all types of Zip drive!

PS when I come to try it out, should I download the IomegaWare drivers for any of my Macs, or will it plug and play on OS 7.6, 9.1 and/or Tiger? (both the Scsi and USB one will work on the G3, so do both SCSI and USB need/not need drivers for 9 and X?) I was a little concerned that those drivers might add a ton of extensions to my slower Macs, so would prefer to avoid them unless absolutely necessary.

 

[wally]

...May I just ask...have you worked for Iomega at some stage?...

No previous association with Iomega. I just happen to have a number of types of Zip 100 drives around the house, and I took apart several Zip conquests recently to repair one and clean another. The more mechanical things you take apart the easier it is to figure out what does what, and how they hide the %$#@! latches and hidden fasteners! And I've been taking stuff apart since about 1960, so I have had lots of practice. [] ]'>