Futaba MR-6C series

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Futaba MR-6C series
BBC Micro Type 1 switch.jpg
Manufacturer Futaba
Family Futaba linear switch
Switch type Linear
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.

Nomenclature

ECPlaza depict the switch with two variants: cruciform mount, and bar mount.[1] 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.

Description

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 It was superseded in Acorn's range by the Futaba low-profile linear switch (in the Electron and Master 128), which was nowhere near as durable.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.

Specification

The known specification, per ECPlaza,[1] is as follows:

Action Momentary
Operating force 100±25 gf
Travel 3.1±0.5 mm
Pretravel 0.8 mm or more
Overtravel 0.5 mm or more
Life 30M
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.

Gallery

The loose switches below were taken from a BBC Micro.

One switch gave its life for this disassembly process.

Keyboards

External links

References

  1. 1.0 1.1 ECPlaza — MR-6C, Various Switches