Futaba MR-6C series
 | |
| 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.
Contents
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 It was superseded in Acorn's range by the Futaba low-profile linear switch (in the Electron and Master 128), which was nowhere near as durable.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.
Futaba simplified linear switches
Switches mounted into a keyboard
Switches are plate mount
Legs unscrew to permit removal of base plug
Base plug removed from the switch
Dual contact leaves (steel and copper), which press onto small lugs
Slider raises the two leaves up against one leg
Steel contact leaf removed
Copper leaf prevents slider from coming out with damaging the leaf
Copper leaf is impossible to remove without damage
Spring recess in the slider contains a small black rubber disc
Shell exterior
Shell interior
All nine components
One switch gave its life for this disassembly process.
Keyboards
- 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)
External links
- Stairway to Hell Forums — Disecting a BBC Micro keyboard keyswitch — including maintenance for weak contact leaves. Dated 2012-05-08. Retrieved 2015-07-27.
References
- ↑ 1.0 1.1 ECPlaza — MR-6C, Various Switches
