Jump to page content

Cherry M7 part number schema

The following page provides known details of Cherry M7 part numbers. The page is split into two main sections:

  1. Gold crosspoint (the original part number arrangement, ca. 1970–1982)
  2. Serie M7 (the new part number arrangement, ca. 1982 onwards)

The information below is sourced from all known part numbers, as listed in:

See Cherry catalogues on the Deskthority wiki for copies of this literature.

See M7 examples for examples found to date.

Unfortunately at present, we still only have a fraction of critital literature. For example, M71 does not appear in the 1974 catalogue, but in fact both M41 and M71 were introduced in 1974. For the former, we have the M71-0100 drawing provided by Cherry USA, dated May 1974; for the latter, we have US patent 3849621, filed in May 1974. Only by obtaining the catalogues from 1975 onwards can we see when these were listed as standard types.

Still required:

Gold crosspoint

It appears that no formal schema existed, and that part numbers were simply assigned sequentially in most cases. For example, 10° stem can be denoted by +10 (as with all the types in the 1973 catalogue, such as M61-0100 and M61-0110) and by +1 (as with M41-0126 and M41-0127). The one known tactile type has non-descript part number M51-0229. However, there are a number of commonalities.

It appears that the T stem was not introduced until later; no mention was made of stem shape in the 1973 and 1974 catalogues, while in 1979 multiple stem shapes exist. The drawing for Burroughs M51-0131—formerly M51-0139—shows a T stem and dates back to 1973, but with nine or ten documented revisions and a Style B shell depicted by the end of the revisions, one cannot be sure what the original looked like. It is not keycap-compatible with normal M7 switches, and it is not clear what led to the introduction of T stems from Alps and Cherry by the end of the 80s.

It is possible that the huge rise in configuration options led to an explosion of non-standard part numbers; that is, it was not possible to define a schema for options not conceived when the series was introduced. (Later options included two extra illumination methods and multiple keystem designs.)

Note however that Style A, AB and B switches with T stems are limited to single pole momentary configuration. The corbel for the T vane of the keystem runs right down inside the slider, and does not leave room for the second pair of contacts (the sliders can only operate one set of contacts). Based on patent drawings, such switches do not leave room for the alternate action mechanism either, which is why B70-05AB has T switches for momentary keys and bar (straight) switches for the lock keys.

By comparison, the style C and D slider is significantly slimmer and supports dual contacts in addition to T and cruciform keystems.

Part number format

Part numbers follow this form:

MSC-0TAB

The positions are as follows:

Position Code Suggested meaning
1 M M: keymodule
2 S Subseries (4, 5, 6, 7); no values below 4 are known to exist, and 8 and above were used for entirely new switch series
3 C The number of contact pairs; this has only been seen as 1 or 2; higher numbers of contact pairs are however known from Serie M7 and could potentially have existed prior to that as non-catalogue parts
4 0 This is always zero in known types
5 T Nominally this indicates the switch type; see the subtypes table below for details.
6 A Undefined
7 B Undefined

Subseries

M4 and M7 appear to be defined by their illumination methods. M5 and M6 are not clearly separated. The following table describes the known switch characteristics within each subseries according to the catalogue listings.

Subseries Stem Force Angle Contacts Action Illumination
M4 Straight, round Various 0° and 10° 1A Momentary and alternate Corner
M5 Straight, T Various 0° and 10° 1A, 2A Momentary None
M6 Straight, T Various 0° and 10° 1A, 2A, 1A+1B Momentary and alternate None
M7 Dual 2–4 oz 1A Momentary Centre

Subtypes

The following table lists suggested subtypes based on the catalogue listings.

Subtype Usage in 1973–74 Usage in 1979–82
0 Unused Various switches; this includes the mechanical shift lock assembly switches formerly in subtypes 3 and 5
1 Standard switches Various switches
2 Unused A handful of assorted switches: the one tactile type, two of the space bar types, and one of the 6 oz switches
3 Used for the shift switch in a mechanical shift lock assembly Unused
4 Unused
5 Used for the shift lock switch in a mechanical shift lock assembly Unused
6 Unused
7 Unused
8 Alternate action
9 Only found in the part number of the only 1A+1B switch (from 1974)

Known parts

The following is the list of known types from the 1973, 1974, 1979 and 1982 catalogues. The descriptions are verbatim per the 1979 and 1982 catalogues. Illumination type and notes are extra to the catalogue.

“✗” denotes parts that are listed as discontinued in the publication in question.

Part Style Stem Force Angle Contacts Action Comment Illumination 1973 1974 1979 1982 Notes
M41-0064 Lighted straight 2½ oz. nom. 1A momentary lens lighted corner
M41-0103 Lighted round 2½ oz. nom. 1A momentary full top lighted corner
M41-0104 Lighted straight 2½ oz. nom. 10° 1A momentary lens lighted corner cf. M41-0123
M41-0123 Lighted straight 2½ oz. nom. 10° 1A momentary lens lighted corner cf. M41-0104; 0° in the 1979 and 1980 price lists
M41-0125 Lighted straight 2½ oz. nom. 1A momentary lens or top lighted corner
M41-0126 Lighted straight 2½ oz. nom. 1A momentary lens or top lighted corner
M41-0127 Lighted straight 2½ oz. nom. 10° 1A momentary lens or top lighted corner
M41-0128 Lighted straight 2½ oz. nom. 10° 1A momentary lens or top lighted corner
M41-0802 Lighted round 2-4½ oz. 1A alt. action full top lighted corner
M41-0803 Lighted straight 2-4½ oz. 10° 1A alt. action lens lighted corner
M41-0822 Lighted straight 2-4½ oz. 1A alt. action lens lighted corner
M51-0106 Spacebar straight 2½-4½ oz. 1A momentary (paddle type)
M51-0107 Spacebar straight 2½-4½ oz. 10° 1A momentary (paddle type)
M51-0143 T 6 oz. nom. 1A momentary non-lighted
M51-0182 T 2½ oz. nom. 10° 1A momentary non-lighted
M51-0226 T 6 oz. nom. 10° 1A momentary non-lighted
M51-0227 Spacebar T 2½-4½ oz. 1A momentary (wire form type)
M51-0228 Spacebar T 2½-4½ oz. 10° 1A momentary (wire form type)
M51-0229 Tactile T 3 oz. nom. 1A momentary non-lighted 4 oz. nom. in the 1979 and 1980 price lists
M52-0104 straight 2½ oz. 2A momentary Possible error? Still refers to M62-0110 for 10°
M61-0025 Shift straight 2½ oz. nom. 1A momentary non-lighted
M61-0026 Shift straight 2½ oz. nom. 10° 1A momentary non-lighted
M61-0027 Shift lock straight 2½ oz. nom. 1A momentary non-lighted
M61-0028 Shift lock straight 2½ oz. nom. 10° 1A momentary non-lighted
M61-0100 straight 2½ oz. 1A momentary
M61-0110 straight 2½ oz. 10° 1A momentary
M61-0120 T 2½ oz. nom. 1A momentary non-lighted
M61-0300 Shift straight 2½ oz. 1A momentary
M61-0310 Shift straight 2½ oz. 10° 1A momentary
M61-0500 Shift lock straight 2½ oz. 1A momentary
M61-0510 Shift lock straight 2½ oz. 10° 1A momentary
M61-0800 straight 2-4½ oz. 1A alt. action non-lighted 2½ oz. in 1973
M61-0805 straight 6 oz. nom. 1A alt. action non-lighted
M61-0806 straight 6 oz. nom. 10° 1A alt. action non-lighted
M61-0810 straight 2-4½ oz. 10° 1A alt. action non-lighted
M62-0100 straight 2-4½ oz. 2A momentary non-lighted 2½ oz. in 1973
M62-0110 straight 2½ oz. 10° 2A momentary non-lighted
M62-0900 straight 2-4½ oz. 1A-1B momentary non-lighted 2½ oz. in 1973
M71-0037 Lighted dual 2-4 oz. 1A momentary top & sides lighted centre
M71-0100 Lighted dual 2-4 oz. 1A momentary top & sides lighted centre Cherry drawing dated May 1974, last revised November 1981

Serie M7

The gold crosspoint switches were renumbered to Serie M7 around 1982. The new switch series of M8 and M9 were given the next available M numbers, and all existing part numbers were rearranged around the highest existing number, which was 7. Gold crosspoint subseries M7 seemed to remain as-is (becoming subseries M71, where the 1 previously denoted a single contact pair and 7 denoted centre illumination), with M5 and M6 being renumbered as M73–74. The corner illumination arrangement embodied in M4 was dropped, being replaced with a much more complex arrangement supporting up to four poles, double-pole changeover (2A+2B BBM and MBB), and the same sprung-lead LED arrangement as seen in Alps SKCC/General Instrument S950 around the same time, covered by M75–78.

The only useful known source of part numbers for Serie M7 is the Cherry Keyboards and Switches Catalogue 1982 (USA), which covers a subset of the range. Four switches from the range are repeated in an undated, unidentified catalogue found by Brother Dragon (yab8433408) that—from the tiny fragment presented online—offers no insights.

The fine details of part number arrangement remain a mystery. There is still a permanently-zero position in all part numbers, and the stem design still appears not to have any formal representation in part numbers. Unfortunately the dearth of example part numbers, coupled with the sharp rise in options, makes this very hard to determine. In particular, there is only one tactile type, only one T mount type, and only one 10° type given in the 1982 catalogue.

Part number format

Part numbers follow this form:

M7S-0TAB

The positions are as follows:

Position Code Suggested meaning
1 M M: keymodule
2 7 7: Series number
3 S Subseries (1, 3, 4, 5, 6, 7 and 8); for details see the subseries table below.
4 0 This is always zero in known types, just as it was prior to the renumbering exercise
5 T Nominally this indicates the switch type; see the subtypes table below for details.
6 A Undefined
7 B Undefined

Subseries

The subseries are divided into three groups. Within each group, the subseries number indicates the number of contacts. The first subseries has one pair of contacts, and each related series after that has one extra pair. For example, M73 has one pair of contacts, while M74 has two pairs. M75 again has one pair, and thus M77 has two extra pairs (77 - 75 = 2), or three pairs in total.

The exact configurations are not known with complete certainty, because the relevant table in the 1982 catalogue is ill-conceived: it does not differentiate between inclusive (e.g. 2A+1B) and exclusive (e.g. 1A or 1B) contact arrangements, which is something you have to deduce and decode for yourself.

Subseries Design Contact pairs
M71 Centre-illuminated (this is in effect the one subseries retained from the prior numbering) 1
M73, M74 Standard switches 1, 2
M75, M76, M77, M78 Complex design that supports up to two sprung-lead LEDs (for which there are dual-window keycaps) and up to four contact pairs 1, 2, 3, 4

The subseries are given in more detail below. The contact arrangements are educated assumptions based on the parts list, because it is not possible to be wholly certain about what Cherry’s table represents. M71 can be ordered with or without a lamp; it is assumed that the LED for M75–78 is optional as it is likely that many customers ordered these only for the extra poles, rather than the illumination.

Note that “1A, 1B” (for example) below means that you can choose between 1A (SPST-NO) and 1B (SPST-NC) while “1A+1B” (for example) denotes both contact pairs being present in the switch (in this example, SPCO BBM).

Subseries Contacts Action Illumination Stem Notes
M71 1A (1 pair) Momentary Lamp Straight, 0° The internal construction likely disallows the alternate action assembly
M73 1A, 1B (1 pair) Momentary, alternate None Straight, T; 0°, 10° Standard single pole switches
M74 2A, 1A+1B BBM (2 pairs) Momentary None Straight, 0° and 10°; T, 0° only Second contact pair occupies the space used by the alternate action assembly
M75 1A, 1B (1 pair) Momentary, alternate LED (single or dual) Straight, T; 0°, 10°
M76 2A, 2B, 1A+1B BBM and MBB (2 pairs) Momentary, alternate LED (single or dual) Straight, T; 0°, 10°
M77 3A, 2A+1B, 1A+2B (3 pairs) Momentary LED (single or dual) Straight, T; 0°, 10°
M78 4A, 3A+1B, 2A+2B BBM and MBB (4 pairs) Momentary LED (single or dual) Straight, T; 0°, 10°

Subtypes

Compared to the prior scheme, the subtype position has very few values.

Subtype Usage
1 Momentary
8 Alternate action
9 Only found in the part number of the one 2A+2B switch; previously it had been used for the one and only known 1A+1B switch.

Known parts

The following is the list of known types from the 1982 US catalogue, with the details cited verbatim (the column headings are simplified for space). The contact pairs column is added for convenience. Note that the M71 types have dual stems which, while being straight as noted, are not compatible with standard 12 mm keycaps.

Part no. Contacts Action Stem Angle Remarks Op. force (cN) Contact pairs
M71-0100 1 A momentary without lamp 85±25 1
M71-0105 1 A momentary with lamp (5V) 85±25 1
M73-0100 1 A momentary 70±15 1
M73-0109 1 B momentary 108±28 1
M73-0110 1 A momentary 10° 70±15 1
M73-0112 1 A momentary for space bar Assembly unit 95±25 1
M73-0120 1 A momentary T 70±15 1
M73-0137 1 B momentary 150±50 1
M73-0176 1 A momentary with tactile feel max. 150 1
M73-0800 1 A alt. action 95±35 1
M74-0100 2 A momentary 95±35 2
M75-0100 1 A momentary 70±15 1
M75-0800 1 A alt. action 95±35 1
M76-0100 2 A momentary 95±35 2
M76-0800 2 A alt. action 95±35 2
M76-0890 1 A/1 B alt. action 95±35 2
M77-0100 3 A momentary 185±45 3
M77-0137 2 A/1 B momentary 95±35 3
M78-0100 4 A momentary 185±45 4
M78-0900 2 A/2 B momentary 95±35 4