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Hirose Cherry Precision

Hirose Cherry Precision Co., Ltd. (株式会社ヒロセチェリープレシジョン; in short, ヒロセチェリー: “Hirose Cherry”, /çiɾosetɕeɾʲi/) was a joint venture between Hirose Electric Co., Ltd. (at that time the exclusive Cherry distributor in Japan) and Cherry Electrical Products.

Contents

Overview

The Company Profile (会社概要) page on the former Hirose Cherry website stated that the company was founded (“創業”) on the 15th of August 1968, and established (“設立”) on the 6th of March 1973. The あゆみ (chronology or milestones) page gave the joint venture as being concluded in March 1973, and the company as being established in May 1973.

Over their lifetime, Hirose Cherry appear to have both imported German switches and manufactured their own switches.

Hirose provided me with a number of old datasheets. These give fascinating insights into their product range, but only cover a portion of the products that we have discovered to date. It appears that there are no documents left at their office that offer a detailed view of each series, in particular all the variant type part numbers. Sadly I am not permitted to publish these datasheets here, even though there is nothing technical given in any of them that we do not already know from other Cherry literature, and despite repeated warnings from Hirose that they are no longer sold.

Switch characteristics

The different Cherry factories approached switch manufacturing in different ways. When two or more Cherry factories produced switches from the same series, they did not operate the same design of tooling, and the internal parts as well as external dimensions could differ. Hirose adopted some very specific differences from the US and German designs.

Keystem

Hirose MX and M8 switches are notable for sharing a keycap mount that is different to those of their Western counterparts. The following diagram shows the various 6 mm and 8 mm keystems; you can see that the Hirose switches share a common mount that is different from the 6 and 8 mm mounts used in the USA and Germany:

US and German keycaps will fit on Hirose switches, but Hirose keycaps will not fit on US and German switches.

No mention is made in the 1988 part number schema for the Hirose keystem. However, the Hirose MX datasheet uses stem type N, and switch type 0.

The keystem features four small protrusions that offer extra grip on the keycap. This design is described in US patent 4123641 “Pushbutton switch” filed in February 1977, along with the corresponding Japanese patent filed in February 1976, but these are not Hirose patents: they are Alps patents. This keystem design is not known from Alps switches.

Contacts

Hirose developed their own switch contact point design. Their contact points are prisms formed from a solid copper or copper-alloy core that passes through the contact or terminal itself. These prisms appear to range from convex-top trapezoid to near semi-circular in section, but such details are difficult to discern. It appears that the top portion of the prism is solid silver alloy, above which there is gold alloy plating. The plating coverage varies, and often some or most of the core remains visible.

View full-size image Hirose M8 and MX stationary contacts (front and back views of each)
View full-size image Close-up of the Hirose M8 stationary contact design, showing the gold-plated copper core of the contact points

The designs of German and Hirose prisms are depicted in the following diagram that shows the cross sections of M8 stationary contacts:

Hirose’s datasheets depict standard US/German triangular prisms, but all production M8, MD and MX switches have been found with Hirose-style prisms. The following diagram shows a comparison of MX contacts:

Switch types

M5 and M6

According to correspondence with Hirose, they started manufacturing M5 switches from 1983 and M6 switches from 1985. There is very tenuous evidence at the moment to suggest that the M5 and M6 switches with trapezoidal holes in the base are Hirose-made switches. The following diagram—which is not drawn to accurate dimensions, being originally a quick sketch—illustrates the observed difference in switch design that could be attributed to Hirose:

The following photos are from eBay seller abc070506. He offers surplus Cherry M61-0100 as a replacement to Amada M61-0120. He retains a single Amada M61-0120 together with its packaging, which demostrates both the part number and that it is made in Japan. (Amada is a Japanese business.) He took an extra photograph upon request to allow us to see what design of base the switch has. This is the only documented example of a Japanese-made M5 or M6 switch, but an extended B70-4753 manufactured after the introduction of Japanese-made M6 switches is another strong clue.

View full-size image Amada M61-0120 switch
View full-size image Part number on packaging (“キースイッチ” simply denotes “keyswitch”)
View full-size image Base of switch showing the trapezoidal holes
View full-size image The Amadan-SS System II equipment to which the parts belong

This theory is not conclusive. Strange patterned marks on trapezoidal-hole M61-0100 sold in the US match those found on US-style M61-0120: thse could be from a manufacturing step common to both factories, but it could also indicate that the holes represent some optional feature of the switches rather than a sign of the factory of origin.

M5/M6 tactile

In 1979, Hirose filed Japanese utility model S56-090326 for a variant of M6 with a tactile leaf. Two leaf styles were shown: one similar to Alps, where the tactile leaf is folded and faces downwards, and one where the leaf is straight and faces upwards:

Curiously, this design pre-dates the point that Hirose claim to have started making M5 switches by several years. It also presents a tactile leaf design before Alps introduced them. (Although Fujitsu FES-8 also introduced tactile leaf springs before Alps, their design was an innovative take on Micro Switch’s sprung pin system, replacing the moving pin and rigid shell step with a fixed pin and moving step, very similar to the stepped contact shape in Datanetics DC-60). The Alps design is different.)

Such switches have yet to be discovered. Tactile types do exist (US-made M51-0229 and German-made M73-0176) but these are likely to rely on steps in the operating cam, not separate leaf springs.

M8, MD, MJ

Hirose manufactured their own variant of M8 series. In April 1983 they also introduced two additional series—MD and MJ—which are essentially M8 with greater travel, 3 and 4 mm respectively. MD and MJ are covered here under M8.

M85

M85, introduced in April 1987, does not appear to be a computer keyboard switch. This appears to be a Hirose product, using again keystem type N (defined this time as “キートップ嵌合先端形状”: keytop mating tip shape).

MX

It was suggested somewhere that Japan got MX switches first; when questioned, Hirose themselves stated that “Originally, German MX switch was based on Japan version.” This would account for the Hirose datasheet using switch type 0 (MX Black is type 1), but it would not explain why a Japanese type would still use keystem N. MD and MJ series use keystem 1, but Hirose MX uses keystem N. The keystem is again shown as German-style but 3.5 mm tall.

The MX patent lists the inventors as Günter Murmann and Günter Bauer. Günter Murmann himself insists that MX is a German design. What we do know is that early Hirose MX switches were branded “HCP”, instead of “Cherry”. Hirose MX switches also use Hirose’s existing contact design from M8/MD/MJ, rather than the gold-plated wire contacts adopted in Germany and the US. Hirose MX switches also use a different design of movable contact, which is the same as that used by the US production line.

See the MX examples page for known examples.

ML

Cherry ML was listed on the Hirose Cherry website. It is likely that these were imported from Germany. They only listed “MLシリーズキースイッチ” (ML Series keyswitch) and “G84-4100シリーズ超薄形コンパクトキーボード” (G84-4100 Series Ultra Thin Compact Keyboard). The pictures were never archived and are now lost.

Capacitive

To date, only one Hirose solid-state capacitive keyboard has been encountered. The design is broadly similar to that of the original US types.

Colour coding

Cherry in the US and in Germany provided large numbers of stock switch models, as well as many custom types. The Hirose datasheets suggest that Hirose only offered a single standard type per series, with every other type being customer-specific. Custom types were either indicated with a dot of paint or a different plunger colour. In most cases, switches with a coloured plunger look to be dyed rather than pigmented, as though standard plungers were dipped into dye vats. Sometimes the same switch can have more than one colour: Yamaha QX3 units have been found with white (clear) switches, orange switches, and a mixture of both, as though the orange colour was only used when there was a risk of confusion within the factory as to which batches of switch were which.

Normally the colours are only seen on MX switches. rzwv found a SORD M23 with pink Hirose switches, which could be M8, MD or MJ. The LED switch under the SMALL key uses a regular white (clear) plunger.

Examples of the various indications of Hirose MX switches can be seen on the MX examples page.