Modding my Leopold FC660C

Hi Friends -

Good evening and happy Thursday. I hope you are well.

I recently purchased a Heavy-6 because I make good financial decisions, so now I am working on modding my FC660C to match the case in all of its endgame glory. My current plan is to install the following: a Hasu controller, BKE lights, and KBDFans 1U Topre to MX sliders on the 1U keys.

With that being said, my questions are as follows:

  1. Is it possible to completely convert an FC660C to MX sliders?
  2. If not, does anyone have leads on where I could buy a set of FC660C modifiers?
  3. Are there any mods that I am missing? I know lubing is a thing, but I want more experience with the board stock first.

Thanks in advance, everyone, and happy clacking!


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MX Sliders seem great, and I’m not discouraging you, but they are super wobbly, even the “better” designed ones from KBDFans. As soon as I modded my 87U, I swapped the old sliders back in, because of the wobble. As for modifiers, KBDFans Topre to MX Sliders should include the stabilized keys, but not for the spacebar. Most people just use the stock spacebar for MX-Topre builds. Lubing reduces the sound, but I prefer the feel of unlubed Topre over lubed.

I agree with yalox, the aftermarket sliders that are offered are too wobbly for my tastes. I had scrapped my Realforce RGB and harvested the stems from there and they’re way less wobbly.

There’s a slight difference between cherry profiles and topre profiles. I’d recommend just switching out the modifiers and just leaving the spacebar as it is. You would have to drill the enter, backspace, and both the shifts.

Good luck with your mods!

Silence-X rings? I use them on the 1U sliders and put bandaids on the stabilized sliders.

Dielectric grease on the stabilizer wires would also help with any rattling.

Thank you for the heads up. My main struggle with my FC660C is the keycaps, so I’m going to give the sliders a go even if they are not a permanent modification. Seriously, the blacked out keycaps may as well not have printing on them for as hard as they are to read in basically every lighting condition (IMHO).

I also have new caps picked out for the board if the conversion is acceptable ( katakana WoB).

Eek, that sounds dreadful. I am not a particularly handy person by nature, so the idea of performing a permanent mod (like drilling) is outside of my comfort zone at the moment.

I am also considering just biting the proverbial bullet and buying a Novatouch to harvest those sliders, but we’ll have to see if I hate my wallet that much.

Could you explain the bandaid mod in a bit more detail? I’ve seen it mentioned in a couple of different places, but I’ve never really understood how to do it myself.

Thank you in advance.

It’s sorta an alternative for o-rings for the 2u keys. Not 100% necessary. You might even find that doubling up on an o-ring has the same effect.

With the mod you cut out a rectangle from the adhesive portion of a fabric bandaid and place it on the inside of the 2u sliders. It’s fine to go over the width but not the length. (Since the fabric will get stuck between the slider and housing)



I just finished converting one of my FC660c to MX today.

I used the KBDFans sliders and some 3d printed stabilizers for the space bar.

  1. No issues with the 1u sliders
  2. The 2u sliders needed a little sanding (I used 220 grit paper) on the long edges to stop them from occasionally getting caught up in the housing.
  3. You need to drill holes in the housing so the stabilizer stems of the stabilized keys don’t impact the housing. I did not do a good job on this and came close to really messing the housings up. You could alternately remove the stabilizer stems from the keycaps if you are sure you are not using them anywhere else.
  4. The 3d printed spacebar stabilizer worked really well, once I made sure it was correctly installed (there is a left side and a right side for the 6u stabilizer). Expensive but worth it. You do need a 6u spacebar with a center stem, GMK sets are generally your best bet, I was lucky enough that /dev/tty supported that config (though I had to source the spacebar from someone else).
  5. The keyboard is noticeably noisier now than with the stock setup. I was not happy with the fiddliness of the KBDfans silencing rings, so skipped them, but may look at a different solution in the future.


Thank you for the in-depth response. I really appreciate it! :slight_smile:

This is what I do also except I use thin surgical tape and Deskey #3. Padding does most of the work but the tape is used to take the sharp edges off the sound made when a slightly off-balance stab side slapping against the case.


Man it so tempting to grab some MX compatible sliders as I’d love to use my MX cap sets with my 660C. Although there just seems to be to many drawbacks to doing so, especially in the feel department. Which is what has stopped me from trying them out yet. I’m pretty sure I got extra lucky with my 660C (it’s the older version, not one of the ones you can get now that I think are made in a different factory). Out of the box it had a super smooth key feel with a pleasant yet slightly loud thock (it was unsilenced stock). In fact the rattly stabilized keys was the only complaint I really had about it, but that was easily fixed by lubing the stabilizers.

Now I did put BKE heavies in it, lubed the sliders/rails with VPF1415, lubed the stabs with 3204, & installed KeyClacks V1 silencing rings (which once again I got lucky with as they have given me no issues although they have been deemed borderline defective!?). So I did do a fair bit of modding to it, but all of that only improved the keyfeel & sound (particularly on stabilized keys). So at this point I am very hesitant to do anymore modding on it as I have it as close to perfect as I think it’s getting for me.

At some point I do plan on grabbing another 660C to MX mod though. As the new ones seem to have worse keyfeel out of the box & seem to take much heavier modding to get up to snuff. So that would make me more inclined to give some type of MX sliders that don’t require me gutting a RF RGB or Novatouch a shot. Really though the best solution would be if Topre gave the option to get all their boards in Topre or MX compatible sliders. They have to know there is a huge amount of Topre owners who are going as far as drilling holes in housings to get MX cap compatibility & I can’t see why they haven’t really taken advantage of that yet beyond their RGB models. I believe the Novatouch slider were a special request by CM so I wouldn’t count them as Topre’s ideal.


For everyone, you can put costar 6u stabs on the fc660c/980c/hhkb. Works very well and is cheaper, easier to install and swap spacebars than the 3d printed version, and easy to find vs novatouch spacebar parts.

Costar 6u stabs on fc660c spacebar

In that pic 2 Stabs were used on each side to keep the wire stable to not move from side to side. You can hotglue them to stay in place.

You can also use 2u Costars + 1u housing for the rest of the stabilized keys, but using KBDFans 2u + drilling the housing is easier and better overall.


Mt3 dev tty

For silencing you need silencing rings (KBDFans, deskeys, keyclack v2) , for overall silence you also need to lube the board. I recommend Tribosys 3024. You also have to lube the inside of the housing and wire for stabilized keys.


This is a wonderfully helpful thread, thank you! I’m embarking on the same path and I’ve gotten to the point of troubleshooting.

The space bar replacement looks a little intimidating but I think I can handle it.

I am looking for some help with silencing my stabilized keys though. I have stock Topre silencing rings on all the sliders, and I see the Band Aid fix, but that seems more targeted at rebound sound right? My stabilized keys have an awful lot of chatter on the down stroke, so I’m trying to figure out how to solve that. I am new to this, so I would really just be taking shots in the dark - I’m hoping y’all could guide me towards what I should focus on.

Thanks in advance!

Since I’m new, I’m not allowed to post links in my posts, but here is a youtube ID of my keys which may help you understand the issue I’m dealing with here:


I added the band-aid bits you suggested, and tried lubing the internals of the stabs, along the wires and inside where they hook into the slider body. It’s definitely better, but nowhere near as good as the non-stabilized keys - which I would argue actually sound and feel just as good as stock. Still a bit of a clack on downstroke. Any recommendations on where to go next?

Thanks again!

Clack on the downstroke of topre is usually related to the wire sliding along the rails on the side of the stabilized keys and slamming against the ends. Have you lubed the stabilizer wires and their channels?

That’s how I’ve solved it on mine

Edit: After rereading, I see that you have lubed the wires and the internals, but I would give it another go maybe just a tiny bit thicker (but not too thick). It can be an annoying process to tune it just right since there is no way to test if it worked until you reassemble the whole keyboard >.<

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Thanks! This is definitely helpful - and explains why there’s an improvement despite it not being “great.” I am using a thin lubricant that I just had on hand, surely the wrong thing so I’ll order the correct stuff and apply a little extra in the channel to hopefully work this out.

Thanks again!