Hi-Tek Series 725
Series 725 (alternatively 725 Series) was Hi-Tek Corporation’s DIN-compliant discrete mechanical switch keyboard series. Linear, tactile and momentary switches were offered; other variants included corner illuminated, alternate action, and higher weight for space bar. The series was created to meet German standardisation. So far there has been no evidence to suggest that switches were ever sold separately. As such, the switch designations remain a mystery, leading to various ad-hoc methods of naming the many variations. (Chances are, the variants would only have non-schematic numeric part numbers anyway, as with the preceding switch types.)
Not long after Series 725 was introduced, it was fully retooled, with the rounded plunger design being replaced with an angular style. One possible theory is as follows:
- Series 725 production was initially set up in the United States
- NMB (later Minebea) moved the production to Thailand
- Shipping the tooling to a new country is time-consuming
- Production in a new factory will take time to get going
As such, it is possible that NMB felt that shipping the tooling to another country would be too much of a risk: it would mean a cessation of manufacturing for an undefined period, as any mishaps with import, installation, production etc. would mean an end to manufacturing output until it was resolved.
From this it could be suggested that NMB had replica tooling constructed and tested in Thailand, built to a revised and simpler design for cost efficiency and ease of construction (perhaps from what was learnt from making the original tooling) and once the Bang Pa-in factory was up to speed, the US tooling was scrapped.
The series name refers to the height at the centre of a home row keycap, measured from the bottom of the PCB, measured in thousands of an inch (0.725″ or 18.42 mm):
(The illustration above was taken by Benjamin Rockwell from an unspecified document provided by Susan Kennedy of Hi-Tek.)
The following details are taken from the RT-8200W brochure. The force and travel figures are standard for NMB keyboards.
|Contact body||Spring temper phosphor bronze|
|Contact surface||Gold alloy inlay|
|Pretravel||0.070±0.020″ (1.78±0.5 mm)|
|Total travel||0.140±0.020″ (3.56±0.5 mm)|
|Operating force||2.0±0.5 oz (57.1±14.2 gf)|
|3.0±0.5 oz (space bar)|
|Tactile force||85.6±14.2 gf (audible click keyswitch)|
|Rated lifetime||100 million cycles|
- Series 725 switch and keycap dimensions (1984), provided by Susan Kennedy (formerly of NMB) and scanned by Benjamin Rockwell
- RT-8200W brochure (October 1997), obtained from the Wayback Machine
- Hi-Tek Series 725 on the Deskthority wiki