Friday, August 10, 2012

IBM Model M (1391401) Bolt Mod / Rivet Replacement (With Pictures)

The IBM Model M is a sturdy keyboard. It's main flaw is that it uses cheap, plastic rivets to attach the main main plastics to the steel plate. These can break over time, and they also pose a problem if you want to access the springs.

I opted to do a bolt mod on my Model M because I was having trouble with a key and needed to access the hammer under the spring. However, if you have any dissatisfactions with the feel of certain keys on your Model M, a bolt mod (and possibly a spring/hammer swap with a lesser used key or new springs/hammers) will probably make it better. I don't notice a huge difference in the overall feel of the board, except that all the keys feel more consistent now. Some people say it has a stiffer feel after a bolt mod, I'd agree with this, but it's not a large difference.

There are several guides on the Internet detailing this process. Essentially, one chisels off the plastic rivets, and replaces them with small bolts and nuts.

I took some pictures during the process, so I decided to write my own how-to guide based on my experiences. Geekhack is a good resource, but it was unavailable during the time I did this mod in July.

If you decide to do this mod, feel free to use my pictures for guidelines, but I'd recommend following one of the guides on Geekhack if you can; they're far more "tested" than mine. Also, there's a pretty good guide over at Overclockers:

---------- Tools & Parts ---------

You could probably get by with similar sized nuts and bolts, but these are what Ripster's guide suggested, and they worked perfectly. So, unless you already have a bunch of supplies that you think will work, I'd recommend getting these exact sized metric nuts and bolts.

---------- Preparation ----------

Get together a table, a towel, some safety glasses, and two identical books that are at least one inch thick (so that the exposed springs don't get damaged after you remove the keycaps). It'd be helpful to get some jars for various parts (springs, keycaps, etc) too.

Take apart the main frame of the keyboard by removing the four screws. Inside, there will be a circuit board attached to the PCBs between the plastic and steel. Carefully disconnected the circuitboard and its ground wire and set it aside for later. Don't lose track of the bolt and nut for the grounding wire. Be very careful not to tear or bend the old PCB plastic.

You should now be left with the steel plate and plastic barrel housing with the PCBs sandwiched in-between. You can remove the keycaps, but DO NOT remove the buttons under the keycaps because it will expose the springs (and you really don't want to damage those).

Chiseling off the plastic rivets.
Start by chiseling off the plastic rivets. There are around 50. Be careful and take your time. Try to cut them as cleanly as possible, it will save you work later. Wear some eye protection, because these things fly off like projectiles and could hurt your eyes. Also, wear some somewhat heavy gloves in-case your knife/chisel slips.

The steel plate separated from the PCBs and plastic housing.
Now that you've successfully flung little plastic circles all over the room, you can lift the steel plate from the rest of the pieces. It's best to stack these pieces in order when you remove them, so that you don't lose track of the order they go in (there are three layers of acrylic sheets).

Removing the rubber sheet revealing the springs.
Once you've removed the PCBs, you can peel away the rubber sheet to reveal the springs and their hammers. At this point, the springs can be safely removed and placed aside for later. If you want to take note of the commonly used springs (spacebar, enter, backspace, etc) for swapping purposes, now is the time. However, I found all but one of my springs to be in nearly identical condition, so I actually only separated the letters from the other keys (in the end, I put them all in one cup anyway, so I don't think it matters all that much).

The damaged hammer in question. It was under the "w" key, it would register a key press before the click. Turns out, the plastic on one side of the hammer had signs of stress, that was enough to affect the key, even after I changed the spring three times.
The removed buttons.
With all the springs removed, you can finally remove the buttons from the board. I don't have a specific recommendation on how to do this, I was able to pop them off with my hands in most cases, but a screwdriver or a flat, rigid object might help with a few of the keys. Once removed, this is the perfect opportunity to clean the keys and buttons. Either run them though the dishwasher or just soak them in some soapy water then dry them off.

Now, it's time to smooth out the remains of those rivets. I used a serrated blade. Sandpaper might work, but be careful not to hurt the little plastic half moons at the base of each rivet.

Using a serrated knife blade to flatten out the remains of the plastic rivets.
With the plastic rivet remains smoothed, it's time to drill some holes! You could probably use a handheld drill for this, but I was lucky enough to find a drill press. If you have access to one, I'd highly recommend using it.

Using the drill press with the 1/16" bit to drill through the rivets.
Use the 1/16" drill bit to carefully drill a hole straight through the remains of the plastic rivets (this is why you sanded/cut them, so they're easier to drill a hole through). 

A few warnings though. Always look before you drill, in one case, there was a plastic piece that holds the little metal bar under a few keys. If you drill through this, you will ruin it. Also, the bolts will get in the way of the two metal supports under the numpad's "+" and "Enter" keys. They're not necessary for keyboard operation, but if you want them, don't drill through here. You might as well leave the farthest right column near the numpad undrilled if you're worried. Also, keep in mind that you're dealing with plastic that is over 20 years old, it can crack and break.

Make sure to go right between the two plastic half moons. A couple mistakes is probably fine (I messed up a few, drilled a bit to close to the edge of the rivet and the screw shows out the side a bit). Oh, and don't worry about the bottom row (near the spacebar), because you'll need washers to complete the bolt mod there.

Finished drilling holes.
One you have a completed drilling, you're ready to start putting things together. With a small screw driver, screw in all the bolts into the holes you just drilled. This will take some time, so be patient.

Finished screwing in the bolts.
In this picture, you can see the little plastic half-moons I was talking about earlier.
Once all the bolts are screwed in, you can start putting everything back together.

Suspend the plastic upside-down between two books. Insert the springs. Make sure it doesn't fall and damage the springs.

Then, place the rubber mat over the springs, followed by the PCBs and, finally, the steel plate.

Now it just needs the steel plate and the nuts.

After fastening the nuts on top of the steel plate, it should looks like this. Don't over-tighten things, your hands are probably almost strong enough. An adjustable wrench can be a livesaver in this step.
After placing a handful of nuts on the bolts, everything will probably hold together. At that point, you can start replacing buttons and keycaps. Now is a good opportunity to test everything before you screw on all the nuts.

Screwing on the nuts is the most tedious, time-consuming step. Take your time and stay calm.

Everything's all put together now!
I had to re-do the nuts a few times, unfortunately, before everything worked right. It's very important that the hammers stay in their place, if they get mis-seated during the process, you'll have to undo all the nuts! Try to avoid that!

Also, I'd recommend that you don't mix new and old hammers and springs. I got a new set on eBay, but they were different enough from the originals, that I could notice the difference. If you need to replace a few, either use the new ones on the F-keys and swap; or get an entirely new set...

---------- Conclusion ----------

I'm very happy I did the bolt mod. This keyboard still has many more years of useful life. The build quality on these boards is pretty incredible, and by doing a bolt mod, you're making it even better.