Repaired a Quantum 40 S full height drive with a stuck parked head!

theirongiant

Well-known member
I would have posted my review of the MacEffects 68030 PDS accelerator for the Mac SE on Friday when it arrived, but my hard drive went on the fritz.

Prior to installing the card, I ran MacBench with all the hard drive benchmarks, then shut down the SE and installed the card.

On the next boot, the hard drive was not recognized.

At first I thought, oh no, I've killed it with the tests. But I could hear the head chugging inside, like it was trying to do something. I also heard the fan speed dip slightly from a voltage sag, which indicated a large but very brief power draw on the 12V rail. The little drive was trying desperately to move something!

I left it alone, and tried again the next day. It magically booted!

Then the next day, it didn't boot.

I had heard about stuck hard drive heads on these old drives, so I watched a couple of videos and gathered my tools and supplies.

- socket wrench, 1/4" drive
- 8mm socket
- Philips #1 and #2 screwdrivers
- Two flathead screwdrivers

I "cracked" the six screws on the case. Note: you must apply a lot of downward pressure while turning avoid stripping the screws. These are on very tight from the factory. Do not use a power drill with attachments. You must do it by hand. And ensure you are always using the correct screwdriver size!

The case is finally held down with a very thin 8mm nut. The screw under that nut MUST NOT be loosened: this one is holding the head in place. I happened to have a set of socket wrenches because I work on my own cars, and have been collecting a lot of tools over the years. The socket wrench made it very easy to remove and install the nut.

Once the drive cover was off, I removed the screws holding the magnet down. Then I used the two flathead screwdrivers to carefully pry up the magnet. Warning; these are neodymium magnets and insanely strong.

With the magnet off, I could see the rubber bumpers. There's one on the magnet, and one inside the drive. I cut a thin slice of red vinyl electrical tape using an x-acto knife and wrapped it around the bumper. This is some kind of tape with a very fine ribbed surface, not your run-of-the-mill black electrical tape, which would have been too thick for this, in sufficiently adherent, and would have suffered the same fate as the rubber in a few years. Painter's tape doesn't hold well enough either.

I gingerly wrapped the pieces of tape over both bumpers. To install the magnet, I carefully lowered it while being sure to hold back as it got closer to the drive body, but making sure my fingers wouldn't get caught. It suddenly snapped into place, so I wiggled it back and forth to ensure the posts were in the sockets. It did finally click once more as it locked down into the proper position.

I reassembled the drive, and voilà ; it worked!

The Quantum 40 S spins at a leisurely ~3000 RPM, and there are no heads on the top platter, so the operation was reasonably safe. No data was lost, and a scan with Lido shows no bad sectors.
 

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superjer2000

Well-known member
I really like these drives - other than this potential issue which is a challenge across a number of drives and manufacturers they are pretty reliable.

One note, I think this is actually a half-height drive, not a full-height drive. It is taller than the later third-height drives though.
 

theirongiant

Well-known member
Ah, I thought the 1" tall drives were the "half height" ones. TIL.

Anyway, this drive is a lot quieter than the shorter hard drives that Apple started using in the LC-series Macs and the Mac Classic II. The motor in the smaller 3.5" Quantum LPS hard drives produces a lot more unpleasant high-frequency harmonics. This one, by contrast, is just a gentle hum. The SE's case fan is louder than the hard drive.
 

Juror22

Well-known member
I cut a thin slice of red vinyl electrical tape using an x-acto knife and wrapped it around the bumper. This is some kind of tape with a very fine ribbed surface, not your run-of-the-mill black electrical tape, which would have been too thick for this, in sufficiently adherent
So you wrapped and sealed the bumper with this - It looks excellent, and since it works that's even better! Which brand of tape did you use (3M Temflex?, WarriorWrap? something else? Could you share a product number if you have it?
 

theirongiant

Well-known member
Thanks!

Here's a couple of photos of the roll of tape. I forget what brand or model it is, and the interior of the roll has no markings.

The only distinguishing features are the ribbing, and the way it stayed deformed when stretched. You can see a very fine "grid" in the red. The adhesive is medium-tack; I'd put it somewhere between painter's tape and duct tape. It sticks to itself very easily, but it doesn't leave a nasty residue the way duct tape does. It does not contain a woven thread like duct tape, nor a fabric backing like gaffer's tape. Due to the deformation properties, this tape does not tear well by hand; you must use a blade or scissors.

If someone here recognizes this tape, please leave a comment!
 

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dan.dem

Well-known member
Ah, I thought the 1" tall drives were the "half height" ones. TIL.
Sadly, I am old enough to remember having used actual "full height" drives (or I should be happy, that my memory still works ;)). They measure 3 1/4 inch in height, not diameter. Typical examples are the floppy drives on original IBM PCs and XTs. Some reference: https://www.computerlanguage.com/results.php?definition=full-height+drive
The first drives I remember being used with Macs had been half height, which became quite common during the second half of the 1980s. The Quantum LPS ("low profile") are 1 inch high, so less than a third of a fill height form factor. I first saw one in early 1991 when I purchased my original Mac LC. And I am still hesitating to try out my old Quantums (I have 5 of them), assuming they are dead now.
 

PB145B

Well-known member
Glad you got it fixed! Always love seeing old drives repaired. I recently repaired a Conner CP3040A 40MB SCSI drive (had the same issue as your Quantum) and it’s currently running great in my SE!

Even though we have modern solutions like BlueSCSI, there’s a certain charm to having a real, period-correct hard drive. Some people just don’t get this, to the point where I’ve had some get borderline angry at me for stating that I “fixed” and old drive, saying I’m “wasting my time” and “you can’t fix a hard drive.” Well, I beg to differ I’m afraid! Some people just love to argue I guess.

My biggest issue with that particular generation of Quantum is they seem to usually have severe stiction. The 80MB one in an SE/30 I sold would get stuck so bad within a few hours, it had to be removed from the computer have violently shaken to get it going again. Shame too, because it worked fine otherwise.
 

theirongiant

Well-known member
AHA. I figured out what kind of tape this is:

Roberts Seam Guard Underlayment Tape


Why do I have this, you ask? Because when we bought our house at the beginning of the pandemic, we tried DIY'ing the floor. We got through half of a room before we gave up and called a professional installer, lol.
 

Juror22

Well-known member
I'm glad that you found this, because my searching, absolutely failed to turn this up! So thanks for figuring it out and reporting back - I have this in my cart already. If for no other reason than I have to get some of my own, so I can decipher the messages imprinted on the tape...
zoom_tape.png
( ...you all see them too, right?)

Using it to fix my drives would be nice also.
 

theirongiant

Well-known member
LOL, the brain sees what it wants to see.

Here's a close up section all stretched out. I think it says "OBEY" 🤣 or maybe just "OOOOOOOOOOOOOO"
 

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croissantking

Well-known member
Even though we have modern solutions like BlueSCSI, there’s a certain charm to having a real, period-correct hard drive. Some people just don’t get this, to the point where I’ve had some get borderline angry at me for stating that I “fixed” and old drive, saying I’m “wasting my time” and “you can’t fix a hard drive.” Well, I beg to differ I’m afraid! Some people just love to argue I guess.

The thing is that there are different approaches to our hobby, and each of us has our own vision as regards restoration and enjoyment. I personally prefer a real hard drive, because it’s authentic and I like the seeking sounds it makes. For me, it enhances the nostalgia ‘feels’.

Unfortunately, I have found it to be a losing battle for the most part as drives keep failing on me and they’ve not been repairable. I’ve gone the BlueSCSI route for my 68k PowerBooks just because working 2.5” SCSI drives are unobtainium; but mostly gone for period-correct drives in my desktop machines (the one exception is my IIci with a ZuluSCSI). The great thing is that you can use server grade Wide SCSI drives with an adapter, and these are widely available on eBay.

The way to do it is to treat spinning drives as disposable and always have a backup handy.
 
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MindWalker

Well-known member
The thing is that there are different approaches to our hobby, and each of us has our own vision as regards restoration and enjoyment. I personally prefer a real hard drive, because it’s authentic and I like the seeking sounds it makes. For me, it enhances the nostalgia ‘feels’.

^ This. I go with spinning drives as long as I have any that work; I like the stepper sounds (not the spinning itself) and in most cases speed is not really relevant. For testing and using pre-made images a modern xxxSCSI stuff is great. Now that I have ZuluSCSI boards that have the initiator mode it's also much easier to do a quick backup copies.

For reference I "fixed" my 230MB Quantum drive with Kapton tape. That's what I had at hand and I thought being as thin as possible would be a good thing. Originally I just wanted to try if I could get the drive working just once to get some files over. The Centris in question now has a xxxSCSI (with the image of the Quantum drive) but the hard drive is also still working.

The part with the neodymium magnet is the trickiest, I borked another drive as the magnet/tool I was using slipped and broke something on it's path.

If the old bumper was easier to remove, I'd be tempted to attempt a 3D-printable replacement with TPU (flexible printable filament). It's somewhat rubber-like (ie. soft) and might work in this role.
 

theirongiant

Well-known member
The part with the neodymium magnet is the trickiest, I borked another drive as the magnet/tool I was using slipped and broke something on it's path.

If the old bumper was easier to remove, I'd be tempted to attempt a 3D-printable replacement with TPU (flexible printable filament). It's somewhat rubber-like (ie. soft) and might work in this role.

Yeah, the magnet plate is a real bitch to remove. That's why I used two flathead screwdrivers placed opposite each other, and levered them slightly away from the head and platters to avoid causing damage. When you set it back down, it might seem like it snapped into place really firmly, but you need to wiggle it a bit to ensure the peg actually drops into the hole.

I spent a few minutes looking at the rubber bumper on the drive to see if it was easily removable, but decided it was not worth risking damaging this particular drive to find out.

I have another Quantum 40 S that came from an Amiga, and this drive is probably unfixable: the spindle wouldn't budge at all until I left the drive in a warm (140ºF) oven for an hour and gave it a good shake to spin the platter. Also, the seek head is definitely stuck to the inside bumper. I'll disassemble that one later to see what options are available for removing the original bumpers. They might just be threaded on tightly, but the melty rubber would complicate an otherwise clean removal.
 

PB145B

Well-known member
The thing is that there are different approaches to our hobby, and each of us has our own vision as regards restoration and enjoyment. I personally prefer a real hard drive, because it’s authentic and I like the seeking sounds it makes. For me, it enhances the nostalgia ‘feels’.
Yes, absolutely. But I’ve literally had people post on threads I’ve started about machines and question why I bothered fixing the hard drive and didn’t “use a CF card instead.” I think that’s so silly.

For example, I had one person on a thread about a laptop I restored that just kept going on and on about how “beneficial” it would be if I used a CF instead of the original drive.

Like, I would never go to another person’s thread about their own machine and question why they were using a solid state solution and insist that they use a real hard drive.
 

MacUp72

Well-known member
I wonder with that replacement of the rubber, does the thickness of the tape actually make a noticable difference in the behaviour of the parking position of the reader head? I could imagine that a too thick tape could prevent the head of making a perfect angle?
 
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