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Alps KCL/KCM Series

Contents

Overview

KCL and KCM were Alps’s DIN-compliant redesign of KCC series. Following the split of series names into separate switch and keyboard series, they were renamed to SKCL and SKCM series switches and KFCL and KFCM series full-size keyboards. In the 1993 and 1994 Alps catalogues, the switches are referred to as SKCL Series and SKCM Series, but the sections on the stock keyboard models use CL Series and CM Series; for example, the 1994 catalogue notes:

抜群の高信頼性スイッチを使用しています。
CMシリーズ(4種類有),CLシリーズ(2種類有)
6種類の中より好みのフィー リングを選択できます。

Very high reliabilty switch is used.
CM Series (4 types available), CL Series (2 types available)
A choice of 6 types shown above is available.

KCL was introduced somewhere around 1983, and SKCL/SKCM appears to have still been on sale into the 2000s. The series included linear, tactile and click feedback; single and double action; momentary and alternate action; and illumination.

An Alps advertisement in JEE, Journal of Electronic Engineering somewhere within issues 205–210 (1984) bears the following summary (reproduced as printed):

ALPS keyboard switches feature smooth operation and a high level of reliability. A wide range of designs is available to meet the varied needs of users. The highly acclaimed KCC Series of key switches is ALPS standard offering. In addition, the KCL Series provided a low-profile 18.1mm-high switch. Together with these two series form a product line it is ideally suitable for the rapidly diversifying office computer, small business computer, word processor and electronic typewriter markets.

The advertisement provides specifications for KCC Series and KCL Series but makes no mention of KCM Series, which is presumed not to have been introduced by this point in time. The advertisement lists the following switch types:

Available operating forces at this time appear to be 80 gf and 90 gf although the text is difficult to read. Google Books will only permit portions of the advertisement to be observed.

Specifications

Characteristic Momentary Alternate action Double action
Rated lifetime 20 million cycles 30 thousand cycles 1 million cycles (stage 2)
Bounce time 5 ms maximum
Contact resistance 1 Ω max. initial
5 Ω max. at end of life
Rated load 12 V DC at 100 mA (1980s, 1993, 1994)
5 V DC at 5 mA (1998)
Travel 3.5 mm 3.8 mm 3.5 mm

Force graphs

Linear

The following chart shows the official SKCLAR (standard 1990s linear model) force graph from the 1993 and 1994 Alps catalogues, overlaid with Jacob Alexander’s measured Alps SKCL Yellow force graph of an unknown switch in unknown condition. Broadly, the two correspond well.

Standard tactile, generation 2

The following chart shows the official force graph used for all standard tactile models in generation 2 onwards: SKCMAP (“SKCM Black”), SKCMAQ (“SKCM White”), SKCMBB (“SKCM Cream Damped”) and SKCMAQ (unknown). The same graph was used in the 1993 and 1994 catalogues and in the SKCLAR/SKCMCQ datasheet from 1998.

Although all these models are rated for 70 cN force, Alps show the actual force level closer to 82.5 cN for some reason. The chart also includes measured force graphs for “bamboo” Alps SKCM White and an unspecified type of Alps SKCM Black, measured by Jacob Alexander. The SKCM Black switch that Jacob measured is close to the published graph but with a peak at 75 cN, while the SKCM White switch only peaked at a mere 55 cN.

SPARC’s measurements of Alps switches came out very differently, with SKCM White having a very sharp tactile peak reaching 65 cN, and SKCM Black having a more rounded peak (similar to the graphs above) reaching around 67 cN.

Owing to the differing (and unspecified) age and condition of the switches that were tested, significantly more examples of each switch need to be measured to get a clearer picture. There may even be differences according to which factory produced each switch.

Rounded tactile

The precise history of tactile Alps switches is not clear, but there is a suggestion that “SKCM Brown” was the first type. This first-generation switch was replaced by SKCMAT, or “SKCM Green”. The measured force curve of SKCM Brown closely matches the published graph of SKCMAT, although a measured new old stock “bamboo” SKCM Green switch shows a rather different force curve.

Models

SKCL and SKCM collectively have a large number of models. The majority remain unidentified, and thus far no original model numbers from the KCL/KCM era are known. The table below contains only the documented models together with their source: the 1993 Keyboard Switches/Tact Switches catalogue (“1993”), the 1994 Keyboard Switches catalogue (“1994”), the 1998 SKCL/SKCM datasheet (“1998”) and a Low-Profile Keyboard Switches sample pack of unknown date (“SP”). The sample pack will be from 1989 or earlier based on the switches it contains.

Known documented (S)KCL/(S)KCM models
SK model K model Type Colour Operating force Generation Sources
SKCLAD Momentary linear Cream 60 gf 1a SP
SKCLAQ Momentary linear Grey 90 gf 2 1993, 1994
SKCLAR Momentary linear Yellow 60 gf 2 1993, 1994, 1998
SKCLFC Momentary linear, red LED Green 1a, 2 SP
SKCLFM Momentary linear, green LED Yellow 60 gf 2 1993, 1994
SKCLFQ Momentary linear, red LED Yellow 60 gf 2 1993, 1994
SKCLJB Alternate action Cream 1b SP
SKCLJC Alternate action Grey 150 gf 2 1993, 1994
SKCLKB Double action White 90 gf, 500 gf SP, 1993, 1994
SKCMAF Momentary tactile Ivory 70 gf 1b SP
SKCMAG Momentary click Blue 70 gf 1b SP
SKCMAP Momentary tactile Black 70 gf 2, 3 1993, 1994
SKCMAQ Momentary click White 70 gf 2, 3 1993, 1994
SKCMAT Momentary tactile Blue-green 70 gf 2, 3 1993, 1994
SKCMBB Momentary tactile, damped Cream 70 gf 2 1993, 1994
SKCMCQ Momentary click or tactile White 70 gf 3 1998

SKCMBB is documented as “ivory” but in reality the colour appears closer to cream. Here it is described as “cream” to accommodate the more ivory shade used with SKCMAF.

SKCMCQ is a mystery. Alps use the same force curve for both click and tactile SKCM models, and they use confusing terminology such as “with tactile sound” for click types and “click feel” for tactile switches. SKCMCQ is classified as a click (“クリック”) type without any further indication. One possibility is that SKCMCQ is the white damped type that did remain in production until something like 2001. If anything, that should have been SKCMBC. The 1998 datasheet lists only SKCLAR, shown as pine, and SKCMCQ, shown as bamboo.

Model SKCLAC is or was stocked by one or more surplus warehouses, but no details are available and the part number is not confirmed from any literature. Possibly SKCLAC was the linear green switch. It would seem that the two standard weights of SKCL were coloured green and cream in the same way as KCC Series.

For the purposes of this table, the switches are classified by generation as follows:

Generation Era Description
1a Pine Full-width slits; only used with original KCL models; no top logo
1b Reduced-width slits, introduced with KCM and used with KCL Lock; no top logo
2 Replacement of most models with new colours; shorter contact modules, and reduced-width slits applied to KCL; top logo
3 Bamboo Removal of slits, and potential cost reductions

In reality, the transition from generation 1 to generation 2 was not a single change, with various intermediate switches existing as Alps redesigned various aspects of the switches. This included SKCMAG-like switches with a white plunger, and SKCLFC with a top logo. The contact assembly moulding also lost its pigmentation shorly before the reduction in height. The generation indications above are simply a rough indication based on the vast majority of switches of each model.

The generation indications above reflect discovered examples, in addition to what is reflected in the product literature.

The table below is a very rough guide to the transitions between switch types. There is too little in the way of discovered literature to have a clearer idea of what was in production in any given year. Generation 3 is claimed to have begun around 1993, although the Alps 1994 catalogue still depicts “pine” switches.

Suggested generation transitions
Type Generation 1 (1980s) Generation 2 (ca. 1990–1994) Generation 3 (to ca. 2001)
Lower weight momentary linear? SKCL Green Discontinued
Standard force momentary linear? SKCL Cream (SKCLAD) SKCL Yellow (SKCLAR) (no known bamboo variant)
Space bar linear SKCL Grey (SKCLAQ) Unconfirmed
Alternate action SKCL Lock Cream (SKCLJB) SKCL Lock Grey (SKCLJC) Unconfirmed
Double action SKCL Double Action (SKCLKB) Unconfirmed
Standard tactile SKCM Orange SKCM Salmon? Discontinued by 1993
Higher weight tactile SKCM Ivory SKCM Black (SKCMAP)
Damped tactile Unconfirmed SKCM Cream Damped (SKCMBB) SKCM Cream Damped, then White Damped
Parabolic tactile SKCM Brown SKCM Green (SKCMAT)
Click SKCM Blue (SKCMAG) SKCM White (SKCMAQ) Uncertain: SKCMAQ or SKCMCQ

The tactile switch transitions are unclear. SKCMAF was rated at 70 gf actuation, as was SKCMAP, suggesting that they are linked. That would suggest that SKCM Orange was followed by SKCM Salmon. Likewise, the association between SKCLAD and SKCLAR is by rated force. Many Zenith keyboards use SKCLAR in combination with a heavier switch—assumed to be SKCLAQ—for space bar.

The relationship between SKCL Green and SKCL Cream is not clear. The Zenith Z-029 keyboard has SKCL Green for normal keys and SKCL Cream for space bar, indicating that space bar is heavier, yet the Epson Q103A keyboard has SKCL Cream for normal keys and SKCL for the LED keys, which would be an odd practice if SKCL Green is lower in weight. The possibility remains that some colours may have been re-used for customised types, just as Cherry did with the MX Series.

Design

LED switches

Momentary linear types generally all have a slot in the top for an LED. This arrangement is not possible with the alternate action, double-action and tactile and click types because the other mechanisms occupy the space taken by the LED. The main body of the LED is 2 mm × 5 mm, and Alps fitted LEDs around 7.1 mm tall that protrude just under 1 mm above the upper surface of the switch. The combination of size and front–centre position are what prevent the LED from being used in switches other than standard momentary linear; by comparison, SMK “second generation” has a circular LED hole in the corner that is only around 2.2 mm in diameter.

The front and rear of the LED each have a flange at the bottom, around 0.7 mm tall and 0.4 mm deep. This flange fits into a step in the shell that prevents the LED sliding out. It appears that the LED can nonetheless be removed while switch is still attached:

  1. De-solder the LED
  2. Push the LED outwards away from the switch, so that the flange clears the step
  3. Pull up on the LED to extract it

This process works fine with a loose switch, but has not been tested with a switch fitted to a mounting plate. The following diagram shows the approximate dimensions of the LEDs found in 1980s SKCLFM switches:

Momentary types with an LED fitted in the factory (F-subseries) also have two holes in the base for the LED terminals, and a recessed area in the front flap to provide clearance. Momentary types sold without an LED fitted used the standard base without provision for an LED. The difference between these two designs can be seen in the illustrations below.

View full-size image SKCLFQ (F-subseries with LED) and SKCLAR (A-subseries, no LED)
View full-size image Matching front appearance with LED removed from SKCLFQ
View full-size image SKCLFQ LED recess
View full-size image Base comparison: note that the Alps logo is relocated to make room for the LED holes
View full-size image Base detail of SKCLFQ
View full-size image Side view of SKCLFW
View full-size image Base comparison
View full-size image LED retention steps at the back and sides of the slot

There is also a small difference with the length of the return spring between these particular SKCLAR and SKCLFQ switches: the SKCLAR return spring is around 1 mm longer than that of SKCLFQ.

View full-size image Internals comparison
View full-size image Return spring comparison

Note that both model numbers are only an assumption. The return springs and weighting differs also between the assumed SKCLAR (red LED) and a confirmed batch of SKCLFM (green LED).

Double action

Alps KCL/SKCL double action is known from Canon typewriters. These switches have two contact modules (“switchplates”), one with and one without its actuator leaf. The module without an actuator leaf is operated by a separate, arched actuator leaf in the plunger, similar to SCK switches. No full disassembly has been undertaken, but the switch has been partially disassembled, and can be seen in the following photos:

Japanese utility model S60-060841 depicts approximately how these switches function, although the bottom of the switch that provides the stiff stage two spring seems to be different in production.

In typewriters, the plunger is colourless. In the 1994 catalogue, one double action model is advertised, specifically model SKCLKB with operating forces of 90 gf for stage one and 500 gf for stage two. This is not necessarily the same model as found in typewriters.

Another model can be seen in the Bravoman arcade machine, advertised as the “ベラボースイッチ” (Bravo Switch). This has an amber plunger. Erwin wrote about them in blog entry ベラボースイッチ特集1(純正スイッチ用ボディ&キャップ製作). An illustration on his blog indicates its operation:

The details are not clear on whether a “big punch” is detected by rapid closing of both switch contacts, or simply by the second pair of contacts closing. The second stage of double-action switches is generally very stiff.

The following images are from aucfree.com; they are still live, but the site itself has died. The images appear to be from a Yahoo! Auctions listing (ID p628617598) from pipinbee, which ran from the 30th of August to 2nd September 2018. There appears to be no way to contact Yahoo! Auctions members even when logged in, and thus no way to ask for permission to use the photos. They are reproduced here as they are the only known clear photos of the switch model.

View full-size image View full-size image View full-size image

The locking tabs that hold the shell closed are not the full width, and the mould cavity number is in very small writing, but both of these characteristics match with double action switches found in Canon typewriters, suggesting that these are genuine Alps parts.

Branding

Original KCL and KCM switches were branded only on the bottom, with the oval Alps logo. Around 1989, the newer block capitals Alps logo was added to the top of each switch. A number of later models were then manufactured without the bottom branding, including pine grey (SKCLAQ), pine salmon, bamboo black (SKCMAP), bamboo white (SKCMAQ) and white damped. A single assortment of switches can contain a mixture of examples with and without the bottom branding.

FD-branded switches

Dr.Click provided some “FD”-branded switches. This confirms conclusively that some Alps switches were manufactured by Forward Electronics in Taiwan. These were found alongside Alps-branded switches with similarly dark blue-grey slider pigmentation in an unidentified scrap keyboard. These are pine and have grey switchplates, indicating that they are neither early issue nor late issue. The photo below of the switches within the mounting plate is from Dr.Click.

View full-size image Switches in place in the mounting plate of the mystery keyboard
View full-size image Comparison of both switch types from the mystery keyboard: “FD”-branded on the left, “ALPS”-branded on the right

FD-branded blue Alps switches can also be seen in the Geekhack topic Alps Appreciation Thread.

Unusual variants

It seems fairly clear that Alps had multiple production lines for SKCL/SKCM switches. Gold Star Alps in Korea appear to have had their own SKCL/SKCM switch production line, with a different colour scheme to that of Alps in Japan. Forward Electronics produced SKCL/SKCM switches, which in rare cases bear their own branding instead of Alps. Some of these production lines did not follow standard Alps practice for mould markings.

The term “scrawly” has been used to refer to SKCM White switches whose mould cavity numbers are written in large characters that sometimes appear to have been manually carved into the mould. The same shell moulds appear to pre-date SKCM White, as SKCM Blue has been found with the same moulds in a Codegen Technology Co., Ltd. keyboard of unknown age (the FCC ID of HMN2YZCG-KB is not on file).

Empty circles

The upper shell of each switch contains one or two circles, that in turn each contain a letter of the alphabet. The purpose of these markings is not known, but it appears to be some kind of batch or shift indication. A number of keyboards manufactured by Datadesk and seemingly also Datacomp used switches where these circles were left empty. Examples include the DSI Modular Pro (a rebranded Datadesk Switchboard) and the distinctly Strong Man–like Datadesk TK-3000 Macintosh keyboard. (The latter, interestingly, uses a model 8031 ROM-less MCS-51 series microcontroller combined with a National Semiconductor EPROM.)

Fake blue Alps switches appear to have been created from these switch shells, using Himake switch contacts; these have retained their historical community name of Simplified Alps Type III for a lack of any better moniker.

Red plungers

A single Toshiba PA5101E Enhanced 102-Key Keyboard is known with clicky SKCM switches with red plungers. This is a standard “Bigfoot” keyboard made by Alps. The encoder date appears to be “8L3” (week 3, November 1988) which corresponds with the “8” (1988) dates on the TTL chips. With the switches being unbranded pine, this would fit. Although it’s conceivable that this is a hoax or a doctored keyboard, it seems more likely that Toshiba had ordered a switch with a heavier or lighter actuation force, something that was never confirmed, although the owner’s perception is that the switches are stiffer than white Alps.

Documentation

References

See also