I’m writing this so that those of you who still have those wonderful Northgate or equivalent keyboards with the Alps white complicated key switches that enable you to type so well at high speeds and simultaneous high accuracy can have an idea of what to do when the inevitable crisis arises: one of your keys stops working or stops working well. Because, crisis it is! You may have backup keyboards that you’ve accumulated over the years, but they aren’t likely to be Northgates, or if they are, they may be in the closet because you they’ve failed in one way or the other and you can’t figure out what to do to resurrect them. And, without a “real” keyboard, well you’re SOL.
(I had a tenkeyless M type keyboard as a backup, but of course when I installed it I immediately had problems because the keys on the right were putting out unwanted characters like 1, 2, 3 instead of j, k, l, and I figured that somehow I had a virus taking over my keyboard. I won’t tell you how long it took me to figure out the real problem. It just demonstrates both how much a crisis it is, and when in crisis mode, the brain stops thinking!)
Resurrecting one of these wonderful keyboards is something of a challenge, especially because there isn’t a lot written about how to do so, although there are some pretty decent resources available that tell you how to take apart the key switches. Yeah, OK, but what now?
It turns out, at least in my experience, that these key switches are indeed resurrectable. You can probably get another 10-15 years of life out of them if you take some care in doing so. Doing so isn’t for the faint of heart, so, if you’re in that league, here’s a shout out to Bob Tibbets at Northgate Computer Repair. Go to his site (
http://www.northgate-keyboard-repair.com) and he will take good care of you, as he did me the first time around. But, as you can imagine, the second time around, one starts to think, “Well, nothing lasts forever. Perhaps I ought to think about buying a decent replacement, perhaps a Matias, but hey, how do I know that it will be the same?” Once you get accustomed to a particular feel of keyboard (whether it be good or bad) over 15 years, moving on to something else isn’t that easy, especially if you can’t test drive it first! I won’t mention the cost issue.
Given that you’re on this web site and you’ve already read this far, it’s pretty clear you’ve got the motivation (and, perhaps, even the skills) to attempt this, so, it’s time to google for help. It’s not like there is nothing out there. But, there isn’t really a how-to for getting to a resurrected state. My hope is that this will provide that and give some insight as to how these switches work in the first place so that you’ll be able get significant more life out of them, and not go immediately into crisis mode like I did.
I’m not a regular poster to these sites, so I don’t know all the details of how they operate and I’m not going to learn them either. So, first you’ll need to find some good images and get an idea of how to disassemble the key switch someplace else. Here is one good set:
http://imgur.com/a/elAFF. Another set that will take you a bit further in the understanding of the key switch resurrection process is here:
http://68kmla.org/forums/viewtopic.php?f=29&t=14993.
First, it is quite unlikely that you’ll need to remove the key switch from the PCB. So, keep your soldering iron cold. But, you WILL need to disassemble the key switch from the top of the keyboard as shown in the above links. To accomplish this you’ll want to get your hands on some fine tweezers, a pair of small screwdrivers, and some decent magnifiers. I use jewelers magnifiers that I can attach to my head with a strap. There are machinists magnifiers that are essentially identical that will do the job nicely. But, you can probably get by with less, especially if through some miracle you’re young enough to not suffer from presbyopia and are a mechanical keyboard enthusiast.
Make sure you can keep the spatial relationships between all of the components clear. The photos are pretty good, but sometimes trying to remember them in the context of what you’re doing is a bit troublesome. You’ll need to have these in mind for reassembly.
Now, for the critical bit! There are two leaf springs in the switch. The more or less isolated one on the “bottom” (as seen when looking at the keyboard in the normal orientation) part of the key plunger doesn’t seem to do much. This is mechanism that creates the infamous click. The other leaf spring is attached to the actual switch mechanism. It’s really hard to see how everything works, but the switch itself is really a sandwich comprising of a pair of gold plated contacts separated by a quite thin plastic film (essentially invisible in the photos) which the tiny arm of the spring pushes against to cause the two pieces of the sandwich to make contact and close the key switch circuit. This leaf spring is attached to the top of the sandwich, but, with care can be removed. If you’re working on a key switch soldered into the keyboard, the sandwich is fixed in its location and should not be moved.
That second leaf spring attached to the sandwich is the critical bit. Apparently, with time, it bends back somewhat and can’t provide enough force cause the sandwich to make contact. The comment about 2/3 of the way down the 68kmla link is critical: “Note that the metal arms should be nearly touching. Otherwise the metal actuator hasn't been bent enough.” In other words, the sandwich leaf spring needs to be bent out enough so that when installed on the sandwich, the fingers that form the inverted V extend past the center of the post in the switch cavity that locates the coil spring. If not, the switch won’t work, or will work intermittently.
I’ve read some commentary about how the Northgate keys lose some of their push-back force over time. This is probably why.
The elements of the sandwich that make contact are gold plated and need to be kept absolutely clean. An aspect of this switch design is that the sandwich leaf spring covers an opening of the sandwich. So when you remove the leaf spring, you need to be sure that you don’t introduce any crud into it. A can of cleaning air is likely to be useful for purposes of blowing away anything that doesn’t belong in the sandwich, and, generally, of the switch cavity.
NEVER, NEVER use contact cleaners or the like. They will leave a permanent residue that will permanently ensure intermittent contact. (Spoken from experience. And, I’m an electronics engineer, and have knowledge of such things. Of course, that knowledge didn’t stop me in desperation the first time around.) If the elements of the sandwich are kept clean, their gold plating is enough to ensure that they will work more or less forever, or at least until the leaf spring relaxes enough so that it needs adjustment again.
In other words, the only thing that you’ll need to do to resurrect an Alps white complicated key switch is to bend out the fingers or arms that make the inverted V enough so that they extend past the center of the post in the switch cavity that locates the coil spring. (Am I being redundant? Well, I once learned about something called rehearsal, a form of repetition necessary for memory formation. And, this point is critical. Sorry if you’re reading this a second time.)
Reassembly is essentially the reverse of disassembly. There is one key issue though: how to get everything aligned properly prior to the final step of pushing the assembly together. One of the thoughts of the guy who wrote the imgur web site was to use a grease of some kind. I’m sorry. I vote NO on that one. It’s a contaminant, and one of the things you want to do is to keep the inside of the switch spotlessly clean forever. You could use a magnet like he also suggested. But the easy method is just to hold the keyboard so that it is oriented vertically and do the assembly sideways. It’s easy. It works, every time. No problem. Now replace the key cap.
That’s it. You’re done. I hope that this helps at least a few people.
