Let’s begin
This is what I started with; an IBM 3278 full size board from 1977 or 1978 in the original un-restored state.
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What is needed to restore the keyboard fully (including the key-switch-cleanup and foam replacement)?
While I got great tips from tron, I wanted to share his list of supplies that you need:
* 15mm Steel Hole Punch
* Paper Towles
* 2mm Craft Foam (I used EPDM foam band with 100mm width and 2mm thickness and adhesive side)
* Tape Measure
* Scissors
* White Marking Pen
* Heat Gun or Hair Dryer
* Containers for The Switches and PCB
* Rubber Gloves
* Work Bench or Table
* Mild Soap and Wash Bucket
* Micro Fiber Wash
* Paper Grocery Bags for Trash
* 3M respirator
* Goo Gone
* Guillotine Cutter
* 3M Acid Free Double-Sided Tape
* Isopropyl Alcohol (really important)
* TIME (take your time with this so you don't have to start over)
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Taking a Beam Spring Keyboard apart is very straight forward. Remove the bottom screws on the case, turn it around and lift of the outer case. You will end up with a view like the first picture.
Next, remove all keycaps using a wire-keycap remover.
The plastic shield beneath them is most likely at a state that you can’t re-use it. In all fairness, it isn’t really required anyway. Remove it carefully. You can also get rid of the initial dirt and plastic shield from the keys.
This is what you likely will have after the first step:
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Be careful when removing those screws. The keyboard might be slipping off the books and switches can dislodge. Once you have it open, you will see something like this:
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If you’re as “lucky” as I am, you will have a completely rotten foam that is looking like this:
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Step 1: Remove the plastic gasket strips
The plastic gasket strips are the ones which have holes for the screws in on each top ridge. I could easily remove them by slowly pull on them. Make sure you don’t rip them apart, but if they contain a ton of goo – don’t worry. Put them aside for now.
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Step 3: Clean the switch plate (get rid of the foam)
The foam originally was on top of an adhesive plastic strip. There are two ways to remove the foam and strip. Either way, get gloves on first (believe me).
Either you use a heat gun and remove the plastic strip together with the rest of the foam (which would be the preferred method) or you do it like I had to do it (the foam was too much dissolved already).
I first removed the foam using a small palette-knife. Look at the picture and get disgusted. This was not funny. After I removed the black foam, I went with a heat gun. With the same palette-knife, I could remove most parts of the plastic strip underneath. Even when I was finished, the switch-plate was still full of goo.
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To get rid of all the glue and dirt from the two strips, place them in a bath of Isopropyl Alcohol. Make sure they are completely soaked for at least 20 minutes. After that, take a cloth and spend a lot of time and effort to make them as clean as possible.
Congratulations at this point you have already reached a point where it starts to get a bit easier and less messy. Put away all parts and concentrate on the Beam Spring Switches.
Beam Spring Switch Restoration
The switches are expensive, please work on them only, if you have enough time at hand.
Preparation:
Get 5 or 6 boxes ready for the parts of the switches. Switch housing, white slider with beam spring, coil and metal stem, O-ring, Fly-Plate.
Below is a picture on the different parts of the switches. I will explain how to take them apart properly.
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There are multiple ways described to take the switches apart. For me, the easiest method was a plastic box which could be taken apart. I drilled a hole into one end that had the diameter of 10mm. This box is only to get a better grip and limit the possibility of damage to the switch (yes, they are expensive).
Now, place the switch in the one half of the box, so that the metal stem and O-Ring are on the outside and the rest of the switch on the inside. Then take pliers, grab the metal stem and pull on it (sometimes as hard as you can). The stem will slide out and the whole switch can be disassembled. As I had to do this about 90 times, I spent half a night on this task. Next, put all the different parts into the various boxes above.
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Plastic Switch Housing:
I put the plastic housing into a bath with mild soap for two days. After that, I cleaned them with a used tooth-brush and clear water. At the end, I put them in an Ultrasonic cleaning bath and finally rinsed them in demineralized water.
Dry them gently and let them sit on a towel for 24 hours.
White slider:
The white sliders accumulated dust and some rust as well. I had to clean them carefully with a tooth brush and mild soap water (look for the beam spring so you don’t damage it).
After the soap water, I flushed them in normal water. Finally, I put them in the Ultrasonic bath and rinsed them in demineralized water.
Dry them gently and let them sit on a towel for 24 hours.
Coil de-rusting and cleaning (+Metal Stems):
Some of my coils have not only been dirty, they also have accumulated rust. Even, if you don’t see rust on your coils at first sight, the de-rusting is super important.
First, clean the coils in mild soap water and make sure that they are dried right after the bath. I cleaned the metal stems at the same time but also used a brush to get rid of the plastic shield sticking to it.
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After the evapo-rust procedure, I cleaned them with demineralized water and let them dry in the sun.
After they have been dry, I put a layer of Ballistol on the parts and let them sit for a day before I used a paper towel to get rid of excessive oil.
O-rings:
The O-rings have been dirty as well, I cleaned them with Soap-water and put them into the Ultrasonic Bath.
Fly-Plates:
I only used some alcohol to get rid of some of the dirt, but did not bath them or anything else. Be very careful with them.
Assembly:
After the procedure I assembled the switches again. This is super easy to do. First take the white slider and clip in the fly plate at the bottom. Then give it a push and the fly-plate should snap up. Put it aside and grab the black switch housing, put the coil on top where it fits in and then drop the O-ring into the middle of the coil.
Next, insert the white slider from the bottom into the housing (there is only one way that works smoothly), so it looks out of the top. The O-ring and coil should be at the outside. Finally take the metal stem and push it into the white slider. The orientation is not important. With a plastic plate I pressed on top of it. There are actually two distinct clicking sounds that tell you that it is firmly inserted. You will see that this needs much less power to do.
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Replacing the foam
Replacing the foam is one of the most important tasks that you need to do. Especially, if the keys are wobbling around. I also found out that the sound is very much dependent on a proper fitting of the switches.
First of all, you need a foam that is cut to a size of 435mm by 100mm (2mm thickness). In my case this was simple, as I already had a 100mm wide band that I only had to cut at 435mm. I used a Guillotine cutter for this to get a very straight cut.
Next, I placed the foam underneath the switch plate so that the side of the foam was looking towards me. You need to align the foam perfectly at this point and I used glue strips to hold it in place.
Next, I turned the switch plate around and started to mark every hole with a white marker on the foam:
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Use the 15mm Steel Hole Punch, place it on top of each marked circle and punch out the hole. In my case, I only had to put some slight pressure on it and wiggle it a bit to punch the holes into the foam:
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I used double-sided adhesive strips to glue them back on. First, I placed the double-sided strips on the edges like shown below:
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Place the switch plate on two larger books in a way that the switch heads can stick out of the holes:
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The re-assembling of the keyboard should be straight forward at this point. Add the keycaps back and you might want to give the case itself a nice paint job as well.
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