Posted By azog on July 26, 2011
Someone recently posted a comment on cleaning the keyboard on an SX-64. The keyboard of an SX-64 is not interchangeable with a C64, so unless you happen across a spare, keeping it working well is just that more important.
I gave it a shot, and decided to take some pictures. Obviously, at least three people in the world have tried this (the commenter, and two people in the referenced URL), so if someone else can make use of this info, that’s just great. Very picture heavy.
First things to keep in mind is that you’re working on plastic that is ~30 years old, and bound to be brittle. A careful hand is necessary, as is patience. If the whole cleaning cycle takes several days, so be it, keeping in mind the serious lack of replacement parts. There are several flaws on my SX-64 from a previous owner, probably just thru wear and tear. I’ll point them out.
First, remove the upper cover of the keyboard. Looking at the edge of the keyboard, you’ll find a gap running around the entire keyboard. There are four clips on the lower edge, around the spacebar, where you can insert a very small screw driver to pop them up and out. Lift the lower edge first, sort of like lifting the hood to a car, because there are additional clips in the top edge, and they’ll pop out better when the cover is at an angle. Here it is with the cover removed.
Once the cover is removed, remove the four screws around the space bar. In the first image above, you can see they’ve been removed. There are two to the left of the space bar, one to the right of the space bar, and one underneath the function keys. I lost one of the screws; my suggestion would be that once you have the keyboard lifted out of the lower half of the cover is to insert the screws into their empty mounting holes.
Once the screws are removed, you can flip the keyboard towards you. This will expose the mounting for the external keyboard connector.
Remove these screws and you can lift the whole assembly out so that you can continue working on it.
Flip it over and you’ll see how each keycap is mounted. They’re simply plastic plungers with two clips on either side; you can depress the two clips per plunger and the plunger will fall right out. Here is the underside with one assembly removed.
Take special note of the space bar. There is a set of three clips, the center clip is the same style as the rest, but each outer clip is a bit different. You’ll want to pop out the center plunger first, and that will make it easier to pop each outside anchor. I also suggest you remove the spacebar first.
This is what each plunger assembly looks like. Very simple: just a keycap on the plunger, a tension spring (which is not visible until you depress the keycap) and the holding clips.
Remove each keycap and stick them in a bucket or something. Due to a construction method that will become apparent later on, I suggest starting from the function keys, working over towards the caps lock key.
As I removed each assembly, I dropped them into a container filled with isopropyl alcohol for a scrubdown later.
Once they’re all removed, you’ll be down to the conductive membrane. Again, be careful here.
There is one screw here, near the soldered cable is mounted to the circuit board. Also, notice the long piece of metal near the function keys. This is the reason I suggested to start removing the function keys first. This bracket will hold the membrane in place as you remove each key. But now it’s time to flip the keyboard over, remove the two tiny screws for this bracket, and set it aside. When you remove the bracket, you’ll see conductive traces underneath it.
Now, GENTLY, GENTLY attempt to lift the membrane up from the circuit board underneath it. The place where that bracket was attached may be stuck a little, so just carefully try to lift it up.
Flip the membrane over, and you’ll see the conductive traces that form the keyboard layout.
Use isopropyl alcohol to wash both sides of the membrane. Do the same thing with the now-bare circuit board that was exposed after you lifted the membrane off.
Now, reassembly is basically the reverse. I actually disassembled and reassembled this twice; the first time, when I tested it, it was acting as if many keys were pressed all at once. I think that is because the membrane shifted around a bit. It seems to be very finicky where it wants to be placed. I suggest that once you place it, and eyeball each opening to ensure that the plunger assembly can be re-mounted, you tape around each edge first.
The tape will help hold it in position. Insert the first screw near the spacebar area first. Be careful not to bind or wind the membrane as you tighten it down. Then reattach the long bracket near the function keys. I worked from top down, inserting the screws from the bottom.
Once you have the membrane in place and screwed down, it’s mostly a matter of reattaching each plunger assembly. Above, I dropped all the keys into a bath so I could scrub them down as it’s time to reattach them. Actually, what I found was that after scrubbing them down, I needed to let the dry, so I just went thru the bunch one at a time, setting each one aside.
They won’t take long to dry.
I started with the spacebar, as again, it’s a special key. Position both outer clips such as this, and then you’ll be easily able to insert it into the appropriate position.
And start inserting each plunger in the appropriate position. Oh, you did take a picture of the keyboard first, so you know where each key goes, right?
Attach the cable assembly to the external port. I cross-threaded the screws and it started to break the plastic. As soon as I heard the tell-tale snap start, I reversed the screw and assessed the damage. Superglue was able to fix it.
You’re familiar with the trick on how to ensure that the screw goes into the original threads? Insert the screw into the hole, but reverse it as if you’re removing it; once you feel it drop or snap into place, it’s in the original threads.
Insert the keyboard into the appropriate slots, re-insert the four screws at the bottom, and snap on the upper cover, starting from the top edge, lowering towards the spacebar. As I mentioned above, the two outer clips are broken off, but there are two inner clips which keep tension.
Ta-daa, nice and clean. Ready to test.