ICL Keyboard with Buckling Sleeves and conductive PCB

User avatar
mmm

10 Jan 2022, 01:13

Long time lurker, first time poster. I recently came across this beauty on eBay. What caught my eye was the nice color scheme, and the absolute level of jank. F-buttons ranging from 1-11, a seemingly lost “) (“ key, stepped keys everywhere and odd clustered mods, not too dissimilar to the ones found on some “newer” Televideo keyboards. I expected to find RMD 973 switches in this keyboard, based on similarity with other boards using this switch, but I was curiously surprised to find them to be some kind of buckling sleeve switches. I’ve not been able to find this switch documented anywhere, which is quite interesting.

Image
The cleaned keyboard

It arrived in dirty condition, but due to the nature of the buckling sleeves “enclosing” the slider, only a little dirt was found on the conductive pads/sliders.

Overview
A 102-button ICL keyboard, that came with the ICL Quattro computer in 85. This was before Fujitsu took over the manufactoring of ICL hardware. I’ve been unable to locate any OEM brand names inside of the keyboard, so I will assume this was produced by ICL in-house.

The keycaps are very thick double shot ABS keycaps in an interesting sculpted profile. It has 11 relegendable function keys, with F1-F11 printed on them - pad printing, I think. The keycap mount is a type of cross-mount, not fully MX compatible. I was able to mount a cap on an MX switch, but this slightly cracked the stem, and the keycap is too thick to go nicely over the housing without hitting slightly, making most keypresses jagged.
Image

The switch: ICL Buckling Sleeves
The switches are conductive buckling sleeves. The buckling sleeve is held in place between the plate and the keycap. The keycap is attached to a slider, which at the bottom of it, has a conductive pad, suspended with rubber in order to give cushioning and overtravel. This results in a very soft tactile switch feel, that actuates around the bottom of the tactile event, and is finally heavily cushioned. I recently tried Topre at a local meetup, and if I remember correctly, the ICL feels quite similar, with a slightly more cushioned bottom.
Off-center keypresses are not handled greatly, and causes increased perceived switch weight. This is especially pronounced on the bottom row as these switches are very curved, and this makes the force applied to the switch angled. This in turn makes me type more heavy-handed than I would type naturally.
The domes themselves have strongly varying force, making some switches more tactile than others. I suspect this is due to wear. When I first received the keyboard, the spacebar was extremely light and sloppy, which was fixed by changing the sleeve.
A single switch is a dummy switch, having an extra plastic element placed beneath it rather than the conductive rubber pad. The “barrel-plate” has a fixed layout, and has inserts on the non-used pads to prevent dust from getting in.

Image
The stem, showcasing the conductive rubber-pad suspended by a small elastic band.

The pcb:
The PCB has a diode for every pad, allowing for full NKRO. There are more pads than there are keys on the keyboard. The pcb states “TSS-Mark III”, that I first assumed to be an OEM manufactorer, but given the lack of search results, I dropped that assumption.

Converting to USB
I located Vcc/Gnd on the pcb and saw that they did not match up with a standard AT DIN plug. The PCB had a leaking capacitor, which explains why my initial attempt at using soarer’s analyzer to decode the signal did not work out. Fortunately the columns/rows are exposed, allowing for a manual conversion. I used a stm32f401-based “Black Pill” as it’s cheap and has enough ports. I desoldered all existing components, added a few extra wires to the PCB, allowing the development board to be mounted directly on the PCB. The PCB consists of 8 columns / 15 rows (or the other way round, if you’d like), which does not give an intuitive matrix, so I didn’t keep count of which columns/rows I wired where, only whether they were columns/rows. I modified the layout slightly, by moving the “dummy-slider” from the bottom-left key, to the “char del” key (two spaces right of F11).

For firmware , I decided to go with ZMK. I’m currently using ZMK in my esoteric 30/40% split wireless keyboards and I like it. I could also have gone with QMK, which is the more traditional choice for wired keyboards at the time of writing. I was lucky enough that Deemen17 had already made a template for starting out with ZMK on a stm32f401-based Black Pill (https://github.com/Deemen17/zmk-config-blackpill_f401), which I shamelessly copied and modified.
For mapping the keymap to the actual layout, I used the ZMK feature of matrix transform. Finding out how to transform the matrix was quite tedious. I loaded up Karabiner-Eventviewer (xed would be a linux alternative), and remapped the keys one-by-one, making many errors along the way.

Conclusion
Very cool keyboard, interesting keyfeel, beautiful keycaps. It has been my first time converting an existing PCB to use a modern development board, and was a fun experience. The varying weight based on sleeves and off-center keypresses makes the keyboard tedious to use, but given all the hours I’ve spent on this, I’ll have to use it. My thirst for rubberbucklers has awoken.

More pictures:
Spoiler:
Image
The "dummy slider" on the pre-cleaned keyboard

Image
Slightly cracked stem on a keycap

Image
Image
The converted internals

Image
Spring-loaded feet (torsion spring)

Image
Feet

Image
PCB pre-conversion

Image
Barrel-plate pre-cleaning

Image
Buckling sleeve on the barrel-plate, showcasing the inserts to prevent dust from getting in.
Similarities with other keyboards
Spoiler:
- IBM Model F AT: Support for additional layouts with additional pads
- BTC Dome over slider: Quite similar design, with the key differences being the use of a buckling sleeve rather than domes, and the conductive pad is less cushioned on the BTC keyboard.
- Keytronic foam&foil with buckling sleeve: This is maybe the most similar keyboard design-wise, where the capacative pcb and the foam is the biggest difference.
Future work
Spoiler:
These are the things that I could do, might do, but most likely will never do.
- Make the “bootloader” button in ZMK work, so I won’t have to press the physical button on the development-board to update my keymap. Currently the &bootloader does nothing, and I don’t know why.
- Experiment with using lubrication on the sliders to decrease friction. Possibly parafin based? done! (but not that nice)
- Rearrange the sleeves according to force/weight done, but lazily
- Lube the damn stabs done!
- Make a typing video
- Detatchable cable done!
Last edited by mmm on 25 Jul 2022, 23:59, edited 1 time in total.

User avatar
Muirium
µ

10 Jan 2022, 10:18

mmm wrote:
10 Jan 2022, 01:13
but given all the hours I’ve spent on this, I’ll have to use it.
Been there! :lol:

Nice first post, and a good project.

Now what about these wireless boards of yours? How do you go about that? I still need to shift some of my abandoned projects from wired to finished wireless.

User avatar
Bjerrk

10 Jan 2022, 10:32

Nice work on the conversion! Love the colour scheme on that board, by the way.

It's a shame that domes like these don't hold up too well over time. Having a similarly inconsistent experience with another dome keyboard at the moment - one with Fujitsu Peerless switches.
Interestingly, there is at least a vague connection, with early Type 1 Peerless switches being sighted in an ICL Keyboard. But I digress.

User avatar
TheInverseKey

10 Jan 2022, 21:32

Wow, nice work I am always been interested in this board thanks for the great writeup.

User avatar
mmm

12 Jan 2022, 00:15

Muirium wrote:
10 Jan 2022, 10:18

Nice first post, and a good project.

Now what about these wireless boards of yours? How do you go about that? I still need to shift some of my abandoned projects from wired to finished wireless.
Thanks!

Currently the wireless boards I own uses a nice!nano, which share's a footprint with a pro micro and is powered by ZMK. The typical boards with a pro micro footprint are not very Deskthority-friendly (Less than 60%, ortho or column stagger). I've been using the Ferris as a daily driver for longer periods.

However if you can do with 21 GPIO pins on a handwire, a nice!nano with a 3.7 LiPo battery should not be too different from a QMK-powered pro micro board. The adoption of wireless and ZMK has been quite fast, and it will only be a question of time before designs that allows for more pins becomes available, I would guess.
Bjerrk wrote:
10 Jan 2022, 10:32
Nice work on the conversion! Love the colour scheme on that board, by the way.

It's a shame that domes like these don't hold up too well over time. Having a similarly inconsistent experience with another dome keyboard at the moment - one with Fujitsu Peerless switches.
Thanks! As you might have guessed, I found out that the keycaps seem to fit almost perfectly on BTC dome with slider boards!
TheInverseKey wrote:
10 Jan 2022, 21:32
Wow, nice work I am always been interested in this board thanks for the great writeup.
Thanks! Glad to satisfy your curiousity

User avatar
Muirium
µ

12 Jan 2022, 09:46

Cool. NiceNano looks rightly nice. Costly, but. Anyone got a discount code for mechboards.co.uk ? :lol:

(I’d have probably just bought one but that coupon code box is taunting me at checkout. Oh commercial psychology!)

User avatar
mmm

25 Jul 2022, 23:57

Update:
I decided to pick this board back up. After trying out some of Bjerrk's Finish Line Ceramic Ceramic Wax Chain Lube, I decided to get some for myself and give this badboy a round. The lube is wet but quickly dries out, making the sliders dry. But it seems like it will only get completely dry after some time.

My initial impressions were that it was super nice and smooth with all the binding completely eliminated. But it's like every time I pick up the board now, I hate it a little more than last time I picked it up. Now it's been three weeks since I lubed it. I wrote the first sentence on the ICL, and I am now typing on a lubed cherry board, which feels like a huge relief. The binding on the ICL has returned, but it's nowhere as bad as it was originally. I suspect that some kind of wet lube would work in addition to the Finish Line lube. Maybe I'll try that .. some day.

I've since then acquired a proto-topre board and a BTC DWS board, so now I have something at hand to compare it to. The ICL is mushy. Very mushy. But when it was smooth, it wasn't a bad mushyness, just the direct opposite of my proto-topre board. Combined with the light weighting (~42g) of the domes it gave a super smooth keyfeel and it felt like I could type at lightning speed and not make any errors. These domes have low tactility compared to both the BTC, and especially the proto-topre.

So now I have sunk even more time into this keyboard, which primary job is to just sit there. But that goes for most keyboards in here anyway, so time well spent 8-)

User avatar
Karmel

30 Jul 2022, 16:29

I had a keypad from a Texas Instruments adding machine with very similar switches to this, I posted it a while ago but I haven't seen any responses to it. These sliders look a bit different and the one I had used springs instead of rubber sleeves, but that rubber mechanism on the bottom seems very similar in operation, kind of like a better version of Mitsumi hybrid switches.

Post Reply

Return to “Keyboards”