Futaba MR-6C series
|Family||Futaba linear switch|
|Sense method||Metal leaf|
|Bounce time||1 ms|
|Actuation force||Ca. 60 cN|
|Total travel||3.1±0.5 mm|
|Keycap mount||Custom cruciform, bar|
|Switch mount||Plate mount|
Futaba MR-6C series (formerly Futaba simplified linear) is a series or sub-series in the Futaba linear switch family.
ECPlaza depict the switch with two variants: cruciform mount, and bar mount. This qualifies it to be considered a series, but it may be a sub-series. No datasheet has been found. The term "series" is used here to clarify that "MR-6C" represents more than a single switch configuration.
The provisional moniker arose from the reduced complexity of the switch over the visually very similar Futaba complicated linear. Despite being a simplified design, at nine components it is still more complicated than switches made today.
Like most other Futaba linear switches, the shell is cylindrical with truncated sides, with a square top above the plate. It sits in a circular hole in the plate. The legs are threaded at the top and screw into place; the base plug of the shell is retained in place by the legs. One leg screws into a hole in the lower contact leaf; the slider presses both contact legs up against the other leg.
This switch is found in very few types of equipment; in most instances of it being identified, the actual switch used is Futaba MD series "complicated linear", which is visually distinct from MR-6C in terms of shape (colour should not be considered). Despite the cheapness of the simplified switch, it proved itself as a robust and durable product, standing up the wear and tear of the United Kingdom's schoolchildren in the 1980s. It was superseded in Acorn's range by the Futaba low-profile linear switch (in the Electron and Master 128), which was nowhere near as durable.
The switch has a non-uniform cruciform slider approximately 4.0 mm by 4.7 mm, with 1.2 mm wide arms, taking a 4 mm deep keycap stem. The distance between the plate and PCB is 12.7 mm. Travel is around 3 mm.
The known specification, per ECPlaza, is as follows:
|Operating force||100±25 gf|
|Pretravel||0.8 mm or more|
|Overtravel||0.5 mm or more|
|Bounce time||1 ms or less (new, and end of life)|
|Mounting pitch||19 mm|
Operating force at 100 gf is likely to be the terminal force, as otherwise it would be too high. This is consistent with all the first-generation switch specifications.
The loose switches below were taken from a BBC Micro.
One switch gave its life for this disassembly process.
- ACC TDD (cruciform mount with complex stabiliser assemblies; 1985)
- Acorn Atom Issue 5 keyboard (cruciform mount)
- Many Acorn BBC Microcomputer keyboards (cruciform mount; 1982–1984)
- Stairway to Hell Forums — Disecting a BBC Micro keyboard keyswitch — including maintenance for weak contact leaves. Dated 2012-05-08. Retrieved 2015-07-27.
- ECPlaza — MR-6C, Various Switches