11
Jan 09Canon Cat keyboard repair
I spent the better part of six years searching for a Canon Cat. When I finally had the opportunity to purchase one in '07, I didn't quibble over price or condition, I was simply elated to have an actual working model.
While the computer itself is in superb working condition, the one problem is with the keyboard. Unfortunately, the Canon Cat was even more impenetrable and monolithic than the original Macintosh, so swapping the keyboard was not an option. The rarity of the Cat meant that neither spare parts nor repair services existed, so I decided to be content with the possession of my machine, if not the actual use of it for the time being.
For the past few months, however, I have been working on a reference design for a new UI, called Lightful, and I have been looking at the best thinking in OS and interface design from the past, going back to Douglas Engelbart's demo that included the mouse and hypertext in 1968, through the Xerox PARC invention of WIMP interfaces, to the Apple Lisa, and of course Jef Raskin's creation of the Canon Cat, so well documented and rationalized in his book The Humane Interface.
I don't have a Xerox Alto or an Apple Lisa (though an emulator was a lot of help), but I do have a Canon Cat. If I'm really going to understand Raskin's work, I realized, I have to use the Cat for daily work for a while. I have to get past the theory and see how it really is to live with it.
That means I have to get the keyboard working. Thankfully, there is a superb group of Canon Cat enthusiasts who provided me with the encouragement to crack it open myself and see if I can't get the keyboard in working condition.
As of today, I've gotten the Cat disassembled, and the keyboard removed for inspection and cleaning. A quick pass at removing the keycaps and trying the switches directly has revealed that I have some level of repair needed, although as of today, I can't say how optimistic the situation is looking.
One user, Hannu Aronsson, has suggested that I begin with some contact cleaner spray, so I will start there, and see how far it takes me.
Hopefully it won't get to the point of desoldering key switches and removing them for cleaning, or worse, but we'll just have to see. I seriously doubt I'm going to find a replacement keyboard anytime soon.
Here is the process so far:
Step 1 – Remove the plastic assembly on the back of the machine. So far, so good.
As soon as the back is removed, I see the telltale splash marks of some liquid long since forgotten. From the color, I'd guess coffee, but it's hard to say. I'll just assume coffee.
The bottom plate comes off next. Seven screws total.
There are three ribbons connected to the mainboard – the power cable, floppy drive, and keyboard. Each one comes up fairly smoothly, though I take my time about it. I'm in no mood to bend a pin or snap any plastic!
Easy does it.
I see more of that brown goop on the side of the metal tray for the mainboard.
The mainboard removes easily, and I set it aside for now. It really is a very compact and nicely designed bit of equipment. Its elegant metal cover reminds me of the way modern luxury cars look when you lift the hood to see the engine.
(That's my Apple eMate and General Magic DataRover in the background, just in front of the Vectrex. All working beautifully, by the way)
The underside of the Cat, with the mainboard removed. I thought I could get to the keyboard now. Nope. It's installed firmly within the top and bottom case assemblies. I try to remove either part of the plastic casing, but something's holding on where I can't get a clear view.
The CRT has to come free next, to allow the case to open fully. It's part of an assembly that I should be able to keep mostly intact. As it transpired, I removed the floppy drive, which wasn't really necessary.
There are two metal covers on the CRT. The one on the back comes free first, with six screws. Next the top metal cover comes off with four screws. I manage to drop one of them into the power supply enclosure. Whoops.
Floppy drive is now removed. Just three screws, it comes out in its sled.
Floppy drive in its sled.
The power cable was very close to the floppy enclosure, and the sled caught on it a bit as I was removing it. No problem, just worth being careful.
I remove the remaining screws that seem to be holding on the front of the plastic casing. It fails entirely to come free in the smooth and easy manner I expected.
The top and bottom of the plastic case are clearly separate, and it looks as though there is a catch just below the CRT that is still holding together.
I spend a fair amount of time jiggling around, trying to see what has to happen for the case to come off. The top tilts forward from the CRT, but it doesn't want to come free.
Finally, after a bit of sliding around, it tilts forward. Nearly off!
It turns out the trick is to slide the whole thing sideways. There is a catch that the plastic slides into and out of.
And it's finally off. I'm holding the machine in my lap now, trying to sort out how to get the next part free.
The rest of the bottom assembly slides free as well – I now just need to get the keyboard out of the final case.
Two screws are all that is left holding the keyboard in place – they were hidden beneath the top half of the case containing the CRT.
To figure out how to remove the keyboard, I spend a while with the whole thing in my lap, lightly exploring what needs to move or come free. It turns out there are two metal tabs on either side that just need to be pressed, and the whole thing slides right out.
The protective covering beneath the keyboard is now fully exposed, and comes off with five screws.
With the protective cover removed, the keyboard itself is finally ready to come out.
Keyboard! I wish I could just order up a replacement…
As I was promised, the keycaps pop off easily. It really is a well-constructed device. Nice springy switches.
Naked keyboard switches. This is really filthy.
Filth!
I'm hopeful that just cleaning it will solve the problem. I decide to try turning the Cat back on with the key caps removed, and see if the keys work any better when I press directly on the switches.
I reconnect all the cables, and power the Cat up. Without the keycaps on, the keys that have been sticking are working fine. I'm encouraged.
I try typing on all of the keys, and things don't look so good, though. Some of them are still not registering keypresses at all, and a few are being less than consistent.
I suppose the next thing to do is try the contact cleaner, and hope that does the trick. I'm not sure where to go next if that doesn't do it. I'm inexperienced with a solder gun, and the prospect of removing individual switches isn't appealing.
One step at a time, for now…