Some hard drive manufacturers used one or more rubber "bump stops" inside of their drives, as part of the head mechanism. In their age, these bumpers can degrade, becoming sticky and eventually melting into goo that will deform with the slightest touch. When this happens, the head-stack will eventually become stuck to the bumper, and then the drive will no longer function. This issue currently mainly affects drives from certain brands made up through the mid 1990s.
When analyzing a hard drive that is not working properly, listening to the sounds the drive is making is the first thing you should do. I've seen two different main failure modes for drives that have this bumper issue. On some drives (Quantum ones usually do this), you will hear a loud rapid head clicking sound that will repeat a few times in cycles. This is the sound of the drive attempting to unpark the drive heads and failing due to them being stuck. Not all drives will do this though. Many will instead spin up and then down repeatedly. I've seen some of the Conner drives do this. Others may simply spin up and stay spinning, with no sound at all from the heads.
While listening to the drive can help, you cannot always tell what the problem is from sound alone. For example, one 3.5-inch Conner drive I ran into that had the problem has a very quiet head seek that is mostly drowned out by the spindle motor. Due to this, I could not get any information based on the sound the heads were making, if they were even making any at all. That drive was also not in a spin up/spin down loop like I've seen with other Conner drives. Regardless, when I opened it up, I found two rubber bumpers in the head mechanism that had heavily degraded, enough that they would deform with the slightest touch.
It is also worth noting that a drive displaying the symptoms outlined above could have a completely different issue that caused the same effect.
Fixing a drive with this issue is both 100% possible in many cases, and can also be quite practical. As you may be able to guess, repairing a drive with sticky rubber bumpers requires opening the drive. Unlike more modern hard drives, the drives that are currently affected by this issue are old enough that they are unlikely to suffer any sort of immediate damage due to being opened, as long as you work very carefully to avoid damaging or contaminating the platters or the head stack.
In a case where the bumpers are only sticky, and not yet completely disintegrating, you can get away with simply placing a piece of tape over the bumpers. This is a good fix if you only need a short term fix, such as if you need to recover data from the drive. As well as that, in some drives, the bumper is small enough, or is designed in a way that you can get away with doing this as a long-term fix. The 2.5-inch Conner drives found in many early 90s laptops are one such example. They have a very small bumper that is located in an area where I believe it is unlikely to be able to cause damage, even if it were to fully melt. Those drives are an exception though, and most other drives will have large enough bumpers that they could contaminate the platters once they get to the point of fully melting. For those drives, you will want to completely remove the original degraded bumpers, and replace them. I've heard of people using heat shrink for this, and you could also probably measure the original bumpers before you remove them in order to find a replacement. It doesn't seem like the drives are particularly picky about what you put there.
Complications to this fix exist for certain drives. The most notable example I know of is the Quantum ProDrive ELS series, very commonly found in vintage Macintosh computers. These drives have a bumper located UNDERNEATH the drive platters, where you cannot get to it. (I also think they might also have one in the head assembly? not sure). You may think that due to this, any ProDrive ELS is doomed to die. This is not the case though! On those drives, you can instead insert a shim into the head assembly to prevent the drive heads from reaching the rubber bumper, preventing them from getting stuck. There is a seller on eBay who has these parts available as of writing. I had a quick look around but could not locate an STL file for any part like this. I think that seller designed the part themselves and hasn't shared it anywhere.
If you know of a source for an STL file for a part like this, send me an email: macdatnet@gmail.com
It's also possible that some other Quantum drives may also have a bumper under the platter. I've only been able to confirm that the ELS model drives have one there though. The ProDrive LPS models do not, and neither do the ProDrive models that preceeded both.
While the rubber bumper issue certainly does cause a lot of grief for vintage computer collectors (especially mac collectors, old macs are full of Quantum and Conner drives!), it is usually a solvable issue. In an age where we have readily available solid-state drive replacements for nearly any vintage computer out there, many will probably choose to just go that route instead of trying to repair a dead drive. But I do know that there are many out there who enjoy keeping the old clunkers around sometimes, myself included. The sound of an old hard drive clicking away is an important part of the vintage computer experience for a lot of people! I hope that this page can help to give a fair break-down on the problem, and how to mitigate it.
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