Futaba MA series

Futaba MA series

Manufacturer	Futaba
Switch type	Clicky, linear, alternate action
Rated lifetime	50M, 10M with LED, 100K(Lock)
Actuation force	60±25 gf, 80±25 gf
Total travel	3.8±0.5 mm
Keycap mount	Proprietary Cherry MX mount
Switch mount	Plate mount

Futaba MA series (formerly Futaba clicky switch) is a series of keyboard switches produced by Futaba and Sejin Electron. The most common form taken is that of a medium stiff, tactile, clicky stacked spring switch. The series encompasses light and heavy weights, click feedback, illumination and alternate action variants.

Nomenclature

Discovery of several model numbers shows the common portion of the codes to be "MA", and as such this is being taken to be the series name until such time that documentation surfaces. The previous name of "Futaba clicky switch" was chosen to distinguish MA series from the various first-generation types collectively classified as Futaba linear switch. While MA series remains conjecture, it provides a name that covers the apparent linear types (heavy momentary) and alternate action types.

History

The Futaba clicky switch (provisional name to differentiate it from their earlier linear switches) was a keyboard switch produced by the Japanese company Futaba. It was in many Korean keyboards, mainly by Sejin Electron. In the foreign market, the keyswitch was first sighted in a 1986 keyboard made by Datacomp in Taiwan. Many Japanese keyboards also made use of the Futaba keyswitch. The last keyboard known to be produced with Futaba switches was the Sejin Electron SKM-1040 left-handed full-size keyboard, which has been re-branded under many different names. Futaba keyboard switches are no longer in production, and Futaba believe that no records remain of any keyboard switch types.

Details

MA series switches are branded "Futaba" on the bottom. Confirmation of identity requires de-soldering the switch from the keyboard. The switch shell is held closed by melted pins; the switch would require glue to reassemble it once the pins have been destroyed. The switch has three legs, in an asymmetric arrangement relative to the branding, with two legs on the left (top-left and bottom-left) and one on the centre right. The top-left and right legs are connected together.<ref name="KBT-EAT-1010" />

The same keycap mount and slider design was later used for the Sejin Futaba-mount dome switch, which used rubber domes over membrane.

The clicky versions use a stacked spring arrangement.

Variants

File:Switch recognition--Futaba--Clicky U mount.svg

Futaba Cherry MX-mount variant

Known variants include:

	Sub-type	Type	Keycap mount
		Momentary, clicky	Futaba (old?)
		Momentary, clicky	Futaba (old?)
		Alternate action	Special
	MA-41	Momentary, clicky	Futaba
	MA-41	Momentary, clicky	Cherry MX
File:No photograph.svg	MA-42	Momentary, linear	Futaba
File:No photograph.svg	MA-42	Momentary, linear	Cherry MX
File:No photograph.svg		Momentary, heavy
	MA-4A	Alternate action, Lock	Special
File:No photograph.svg	MA71	Illuminated, clicky
File:No photograph.svg	MA72	Illuminated, linear

Most Futaba clicky switches have an inverse cross mount, i.e. the cross is on the keycap, and the slot is in the slider. The keycap stem and the slider each have a two-stage mount, with a smaller cross followed by a larger cross. These switches have been found with white and cyan sliders. Sejin-made keyboards typically use this slider.

There is also a much less common variant with a Cherry MX-compatible slider; these are found in several Chicony keyboards (including some KB-5161 and some KB-5181) and in some Focus keyboards.

The keycap mount is not believed to be indicative of any difference in keyfeel.

The slider colour does have significance, but the details of which are not well documented. Cyan and blue are reported to feel and sound different.<ref name="KBT-EAT-1010" /> At least two keyboards have been found with a stiffer switch used for the space bar, with a dark grey slider<ref name="ScarFace" /><ref name="Microweb" /> or a cyan slider<ref name="Packard Bell XT" />.

There is also what appears to be an older variant with a different slider. This variant is welded closed along the sides, and is found in the NEC PC-8801-KI.

Specifications

Four series, model or part numbers have been recovered, along with their specifications.<ref name="ePartsHub-MA41-MA42" /><ref name="ePartsHub-MA71-MA72" />

The keycap mounts for these switches are neither described nor depicted, and the well-known latching version is not listed.

Characteristic	MA-41	MA-42	MA-71	MA-72	MA-4A
Action	Momentary
LED	No		Yes
Tactile feedback	Yes	No	Yes	No
Operating force	60±25 gf, 80±25 gf
Travel	3.8±0.5 mm
Pretravel	0.8 mm or more
Overtravel	0.7 mm or more
Bounce time	5 ms max (throughout lifetime)
Mounting pitch	19.05 mm
Lifetime	50M		10M
Specification	FS-6015A4	FS-6016A4	FS-6007A7	FS-6016A7

The MA-41 [sic] switch specifications are also found in the Sejin Electron SKM-2040 User's Manual; here the switch lifetime is given as 10 million cycles, and the bounce time as 10 ms.

The specifications are written out as unformatted text, which loses some clarity. As a consequence, the distinction between MA41 and MA42, and MA71 and MA72 isn't clear. Since the heavier space bar switches in keyboards do click, the reasonable interpretation is that both weights apply to each of the clicky and linear switches.

The existence of a momentary linear version of the switch has long been in dispute. Sejin Electron SKM-1040 is specifically reported by a reseller to be linear, and this would fit in with the interpretation of MA42 as the linear equivalent to MA41. Most reports of linear<ref name="Linear" /> and tactile<ref name="GH_nctactile" /> versions of the switch are likely referring to worn switches that no longer click.<ref>YouTube — Sejin 2040LH Futaba Switch</ref> Such switches have never been examined internally as they cannot be opened non-destructively.

The alternate action version is however confirmed to use a different contact arrangement that appears to be linear, and this may be what is used inside MA42 and MA72.

Keyfeel

The Futaba switch design typically encountered is a clicky and tactile switch. The keyfeel has high hysteresis, with the actuation click occurring around 2.5 mm into the approximately 4 mm travel, and the release click occurring at 1 mm from the home position. The switch is very smooth, with a gentle rise in force, and only a small decrease in force after actuation. The switch has been demonstrated to have a loud ringing sound on a variety of pitches, like a higher-pitched IBM Model F.<ref name="YouTube-SKM-2001" />

Keyboards

Early type

• NEC PC-8801-KI
• NEC PC-8801mkII

Later type

Clicky

Proprietary / White Inverse Cross mount

• Some Chicony KB-5160
• Datacomp DFK-501F/502F (cyan for space bar, grey for enter)
• Datacomp DFK-555
• Datacomp DFK-777F
• Microweb Touch-1
• Olivetti M15 Laptop<ref name="olive"/>
• Packard Bell XT keyboard (Sejin Type #: M7US02X-20, FCCID: GJJ4AKM-8700DE)<ref name="eBay-Packard-Bell-XT" />
• Sejin Electron EAT-1010 (cyan/grey for space bar)
• Sejin Electron SKM-1040 & SKM-1080<ref name="Sejin_1080"/>
• Tatung TCS-5000

Cherry MX mount

• Some Chicony KB-5161/5162
• Some Chicony KB-5181/5182
• Some Chicony KB-5191/5192<ref name="Chicony KB-5191" />
• Focus FK-1001
• Some Focus FK-6000 & FK-8000
• Some Leading Edge AK-1012
• Sigma APO System AFK-7711<ref name="sigma"/>

Linear

• Sejin Electron SKM-1040

Gallery

Futaba mount variant

• 
  Futaba switches in a Datacomp DFK555 keyboard
• 
  Disassembled switch
• 
  Additional view of the internals
• 
  Cyan space bar switch in a Tatung TCS-5000 keyboard
• 
  Grey space bar switch in a Sejin Electron EAT-1010 keyboard

Cherry MX mount variant

• 
  Cherry MX mount variant
• 
  Base showing branding and asymmetric leg arrangement
• 
  Rear
• 
  Left-hand side
• 
  Right-hand side with exposed metal
• 
  Tai-Hao Cherry doubleshot fitted
• 
  Bottom view of switch and keycap
• 
  Switch and keycap

Early version

The following is not confirmed to be the same switch as the regular Futaba clicky switch, as the internals are not known to be documented.

The switch is designed to support an external conical spring to provide extra weight.

• 
  Front
• 
  Side
• 
  Heavy and normal, top
• 
  Heavy and normal, front
• 
  Heavy, side
• 
  Side view, showing welded shell
• 
  Base view
• 
  Two different gauges of external spring (ca. 0.25 mm and 0.5 mm) giving 20 gf and 190 gf extra force respectively (from an NEC PC-8801mkII keyboard)

References

<references> <ref name="ePartsHub-MA41-MA42">ePartsHub — MA41,MA42</ref> <ref name="ePartsHub-MA71-MA72">ePartsHub — MA71,MA72</ref> <ref name="YouTube-SKM-2001">YouTube — SEJIN SKM-2001 ADB KOREA FUTABAスイッチ キーボード Dated 2012-06-01. Retrieved 2015-07-26.</ref> <ref name="eBay-Packard-Bell-XT">eBay — Vintage Packard Bell XT Keyboard Made in Korea Works (DEAD!)</ref> <ref name="KBT-EAT-1010">KBtalKing — ■鍵盤史的遺跡SEJIN EAT-1010(FUTABA軸)■ (Chinese only) Dated 2009-01-08. Retrieved 2015-07-26.</ref> <ref name="ScarFace">ScarFace Keyboard — 리딩엣지 - AK 1012 (Korean only) Dated 2010-02-05. Retrieved 2015-07-26.</ref> <ref name="Linear">Deskthority — Futaba or modern equivalent</ref> <ref name="GH_nctactile">Geekhack — new in box alps Posted 2009-12-20. Retrieved 2015-07-26.</ref> <ref name="Microweb">Deskthority — Microweb Touch-1</ref> <ref name="Packard Bell XT">Reddit — Old Packard Bell XT Dated April, 2014. Retrieved 2015-07-26.</ref> <ref name="Chicony KB-5191">Reddit — [1] Dated September, 2017. Retrieved 2017-09-23.</ref> <ref name="Sejin_1080">egloos — Sejin SKM-1080</ref> <ref name="sigma">Imgur — Sigma APO System AFK-7711 (Futaba MA) Uploaded 2022-06-09.</ref> <ref name="olive">Imgur — Olivetti M15 Laptop (Futaba MA, Inverse Cross Mount) Uploaded 2022-12-24.</ref> </references>