EDIT March 19th, 2015:
What you will find here is the FIRST version of my method for silencing the upstroke on Topre keyboards.
I have since greatly improved the method by adding a step between steps 4 and 5 below: I use a clothing iron (yes, seriously) to make the landing pads very thin, around 0.15 to 0.20mm (0.006 to 0.008inch).
You will find in the discussion thread that some people have complained that my original method reduced the key travel too much, and that some of the switch tactility was lost. This can be completely fixed by ironing the landing pads. There is a little bit of play on top of the Topre switches, and the thin landing pads can fit there.
With the new method, there is NO REDUCTION IN KEY TRAVEL, and THE SWITCH TACTILITY IS COMPLETELY UNCHANGED. The keyboard is just much more silent.
The method below (and the improved one with ironed landing pads) can be applied to almost any Topre keyboard, including:
- The Leopold FC660C (as shown below)
- The HHKB Pro 2
- The Realforce (all versions)
- The Novatouch
My method is not useful for Topre Type-S (silent) models. The mod I describe below has already been done at the factory on these models, except that Topre uses a thicker sound dampening material, and has to use different switch stems to compensate. My mod provides approximately the same noise reduction on the upstroke than the Type-S models. The bottoming-out noise is affected neither in the Type-S nor in my mod, it's still the now legendary "Thock".
In this post I will show how to turn your Leopold FC660C into a Type-S FC660C.
I love the FC660C, but to be honest I don't like the sound of non-silenced Topre switches.
The "Thock" part is great, but the "Clack" on the upstroke sucks.
On Cherry switches (reds and browns), I use grease (a lot of it) to dampen the sound on the upstroke. It works well but it changes the feel of the switch.
On Topre switches, it takes a lot more work, but the result is really worth it and it does not change much the feel of the switch, which is a good thing.
I did not invent the method. I have read it from several sources, when it was applied to the HHKB. I have just applied it to the FC660C and as I have not seen it documented anywhere else, I thought I should do it.
To silence the board, you will need to disassemble it almost completely. It's not too difficult, but it takes some time. The mod took me 4 hours, but I did some tests during this time (with O-rings and soft landing pads). I think it can be done in 2 or 3 hours.
In the following video, you can hear the difference between silenced keys (the two top rows of the keyboard) and the non-silenced ones (two bottom rows):
(This may play upside down, and I'm sorry if it does)http://www.chesstiger.com/images/keyboards/Silenced_FC660C.mp4
For the mod, you will need mainly the soft landing pads sold by EliteKeyboards, or some equivalent.
Here is a link to the product: http://elitekeyboards.com/products.php?sub=access,slpads&pid=sl120_cs
These pads are normally used in Cherry MX switches to dampen the sound of the bottoming-out (downstroke). Here, we are going to use them to dampen the sound of the upstroke in Topre switches.
O-rings will not work for the purpose. I'm going to explain why later.
Ideally, you will also need some stabilizer grease (high-viscosity lubricant), like this one from EliteKeyboard: http://elitekeyboards.com/products.php?sub=access,misc&pid=mechlube
NOTE: the feel of the Topre switches is SLIGHTLY altered by the mod. The travel of the keys is very slightly shortened. In my opinion, the pleasure of typing on Topre switches is still 100% there, and the reduction of the upstroke noise makes the board sound much better: the board just "Thocks" and doesn't "Clack" anymore. However you may want to try the mod on a single row of the keyboard at first, just to see if you like itů Anyway the mod is 100% reversible. You can go back to the original feel of the keyboard at any time if you don't like the mod.
Here is the procedure:
1. Unplug then disassemble the keyboard. You will first need to remove the screw located under the circular "Quality Control" sticker. It's under the keyboard, approximately under the Enter key. Then you need to un-clip the top part of the case. When you look at the bottom of the keyboard, you will see the holes where you can insert a flat screwdriver. You may need several of them inserted at the same time to be able to remove the top of the case (I have been able to do it with a flat screwdriver and a plastic ruler but it was no fun).
When the top of the case has been removed, the keys and the PCB remain connected to the bottom part with a flat (ribbon) cable. You need to unplug this cable. It has a small connector that can be plugged and unplugged many times without damage. You will need a small flat screwdriver to take to two parts of the plug apart. I forgot to take pictures of this stage, sorry about this.
2. Once the connector has been unplugged, the work on the mechanical switches can start. At the back of the PCB you will find approximately 25 screws (!). The silver ones are screwed into the metal plate, the black ones are screwed into the plastic housing of the keys. Remove them all. You don't really need to remember where they come from: the black ones are marked with a white arrow on the PCB, the silver ones are marked with a circle. There is only one size for each type, so just unscrew them all and be confident that it will be easy to put them back later.
(I had already removed some screws)
3. Now you have two parts: the PCB with the cloud of boobs, and the metal plate with the plastic switch housings. Be careful not to remove the rubber domes. They are lightly glued to the PCB, but they can be removed a little bit too easily. I know, because it happened to me, and then it was not easy to put back the dome and the conical spring exactly where they had to be. You are going to work only of the metal plate part, but you will have to put it back on the PCB sometimes and that's when you could move a rubber dome by accident.
4. In this picture you can see the switch housings.
Inside every of them you can see the plunger, a small part with two rectangular holes. They also have two small legs on opposite corners. We are going to put a soft landing pad on the stem of every plunger, so it will look like this, seen from the side:
And seen from the top:
The idea is that when the plunger goes up during the upstroke, it will not hit the plastic housing. The landing pad will absorb the shock, and reduce almost completely the "Clack" on the upstroke. The travel of the key will be reduced by less than a millimeter, which does not affect much the feel of the Topre switches.
Some of you may ask if it is also possible to use O-rings. I have tried, and the answer is: almost. Here is how an O-ring on the plunger looks like:
When the O-ring sits like that, it works well. However, O-rings tend to have a life of their own on lubricated Topre stems, and after a while some end up like this:
And when it happens, it is bad because the key cannot go back all the way up. You get a dead key. This has not happened to me with landing pads, so I recommend landing pads.
What you need to do right now is put a landing pad on the stem of every plunger. But to do this you need to remove the keycaps. We could have done this before disassembling the keyboard, but I chose to do it while the keyboard was disassembled because I wanted to test what I was doing and that implied removing and putting back the keycaps several times. That's how I was able to test O-rings and find out that they did not do the job.
To remove the keycaps, just put the metal plate back on the PCB. The rubber domes will push the plungers and you will be able to use a keycap remover.
5. Now we need to eject the plungers from the plastic housings. Do this only for the keys that do not have a stabilizer (we will see how to handle them later). When the keycaps have been removed, you need to push quite hard with either the tip of your finger or with a screwdriver on the plunger to eject it:
The plunger will pop out of the housing and you will be able to equip it with a soft landing pad as pictured above. Then you put back the plunger inside the housing.
IMPORTANT MESSAGE FROM CAPTAIN OBVIOUS: two opposite corners of the landing pads must be aligned with the legs of the plunger. If they are not, the landing pad will block the plunger and the key will not work.
6. The keys that have a stabilizer are more difficult to mod. In this picture you see 3 of them:
They need to be completely disassembled and ideally even removed from the metal plate.
They are inserted in the metal plate by force, so you can remove them by inserting a small flat screwdriver between their plastic housing and the plate.
Here is the housing of a key with a stabilizer, removed from the plate:
Around the hole in the metal plate, you can see that I have applied some stabilizer grease (high viscosity grease). This will reduce some noise caused by the play between the housing and the metal plate. To be honest I'm not sure this step is required, so maybe you do not need to remove the housings from the metal plate.
To disassemble the stabilizer, use a screwdriver to unclip the middle of the wire out of the housing. You will then be able to disengage the bended ends. Only then will you be able to remove the plunger.
You can see that the plunger of the stabilized keys is different: it is much longer. This will force us to use more than one landing pad. In the image above you can see one possible way to do it: two halves of a landing pad are glued inside the housing. However, this is not my preferred method. Below you will see a better way to do it:
Two halves of a landing pad are glued directly on the plunger so they extend the one that is placed around the stem. This prevent the right and left part of the long plunger to hit the inside of the housing on the upstroke.
When you have done this, you can reassemble the stabilized key housing and force it back into the plate hole. It is also a good idea to add some stabilizer grease at both ends of the wire.
Fortunately, the space bar has a stabilizer wire but is very easy to mod. You just need to put a landing pad around the stem of the plunger and put some grease at the end of the wire. Please note that the space bar has a special spring, just don't forget to put it back in place before inserting the space bar keycap.
When you have put landing pads on all the plungers, you can just reassemble the keyboard and enjoy the sound!
Before you screw back all the keys on the PCB, it may be a good idea to reconnect the ribbon cable, put the plate with the keys and keycaps on the PCB and connect the USB cable of the keyboard to test if every key is still working. If a key does not work (probably because a rubber dome has been moved), at least you will not have to remove all the screws again.
Credits (these were about silencing the HHKB): https://geekhack.org/index.php?topic=40582.0 https://geekhack.org/index.php?topic=34972.0 http://www.key-bored.net/hhkb2-silencing-mod/
My apologies for all "prior art" I have failed to mention.