Hi-Tek High Profile

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Hi-Tek High Profile
Manufacturer Hi-Tek Corporation
Switch type Linear
Sense method Metal leaf
Switch mount PCB mount
Patents US3751618 (1972)

Hi-Tek High Profile, formerly referred to as Hi-Tek linear, is a family of switch grids from Hi-Tek Corporation.

Nomenclature

"High Profile" (also referred to as "Hi-Profile") is believed to be a retronym introduced by Hi-Tek following the introduction of Hi-Tek Series 725; prior to this, these switches seem to have had no series name.[1]

Description

The design depicted in the patent, with circular sliders, was designed for calculator keypads. In order to support full-size keyboards, a new grid system was introduced, made from discrete single-key mould units that could be assembled to mould entire keyboards; prior to this, it seems that the mould layout was entirely static.[1] Thin ridges around the grid walls demonstrate where the mould units are placed together to generate the overall grid moulding.

Each switch position takes up the entire unit. Since the contact and slider portion only needs to occupy the centre, the rest of the assembly is mostly empty space, with a wall around each switch position and bracing struts up to the centre shaft. The appearance of this largely-empty grid earned the design the nickname "waffle frame".

The switch contacts are a pair of vertical leaf springs placed side by side, that are held apart by a horizontal bar in the slider. When the slider is depressed, the bar is lowered and the contacts close. The slider is hollow, and the contacts are exposed when the keycap is removed. The return spring has a tight cluster of turns in the centre as well as at each end; this and the general design of the contacts are both found in the successor Hi-Tek Series 725.

Slightly prior to Series 725, Hi-Tek later introduced Dovetail Series, a modular, interlocking revision of the High Profile design that allowed for easier and cheaper construction of custom keyboards. Instead of requiring a full custom mould arrangement for each new keyboard, discrete and semi-discrete switches together with spacers could be joined together to form a larger grid.

Recognition

In many cases, Hi-Tek supplied only the switch grid, leaving the customer to supply the PCB and logic circuitry.[2] The result of this is that may Hi-Tek switch grids have no branding; branding on the original-style switch grids is extremely rare. Hi-Tek as a manufacturer is generally confirmed by branding on the PCB, in the instances where Hi-Tek supplied complete keyboard assemblies.[3] With flat-top grids, however, the Hi-Tek branding is placed above the space bar.

As Stackpole grids are also frequently unbranded in the same manner, this created much confusion about differentiating Stackpole and Hi-Tek grids. However, the distinctions between the two now seem fairly clear.

Variants

Waffle frame, black

These switches are often found in DEC terminal keyboards. The separator bar in the slider features an "island", a raised area with semicircular ends. This raised area often contains three dots in a row, which appear to be artefact of the manufacturing process as they can be misshapen, found either side of the island, or simply absent. The purpose of the island is not known, although it may increase the pretravel and actuation force very slightly.

Waffle frame, colourless

This is very similar to the black variety, but the separator bars lack the island in the centre.

The example below is from a Hewlett Packard 2623A keyboard.

Crenellated

The crenellated version is not confirmed to be Hi-Tek. It seems to be specific to the DEC VT100 keyboard, although that keyboard also uses regular black sliders.

The top of each slider is flared, and a rectangular notch is cut into each of the four sides. No explanation for this variation is known.

Flat-top

Flat-top switches are effectively the same as the colourless-slider waffle frame grid, but the switch positions have a top surface to them instead of an open grid frame. These grids tend to have the branding and patent number in the centre by the space bar.

Servicing and parts

Computer service manual findings show that, as the switch grid is monolithic, there were provisions made to service individual switches. Each switch component was assigned its own part number, and an insertion tool was available to assist with insertion of replacement contacts. Section 5.6.6 of the Lear Siegler ADM-3A maintenance manual contains an illustrated guide to replacing a pair of switch contacts using the insertion tool. This in itself appears to confirm that the ADM-3A keyboard was supplied by Hi-Tek (unless Stackpole used Hi-Tek part numbers).

The following part numbers have been found:

Part Part numbers
Plunger, momentary 173-40213 (NABU 3100)
Plunger, locking 173-40334 (NABU 3100)
Cam, locking 173-40260 (NABU 3100)
Spring, 2 oz none (NABU 3100)
Contact, solid 173-30107 (NABU 3100)
373-30052-2 (LSI ADM-3A)
Contact, fingered 173-30108 (NABU 3100)
373-30053-2 (LSI ADM-3A)
Tool for contact replacement 173-10023 (NABU 3100)
Stabiliser wire (8 units) 373-10020 (CDC IST II)
Stabiliser wire clip 373-30104 (CDC IST II)
Stabiliser insert 373-30105 (CDC IST II)

The NABU 3100 (formerly Volker-Craig VC3100) keyboard has yet to be seen, and it may be that some of these parts are specific to Hi-Tek Dovetail Series.

The CDC IST II service manual also cites a 2 oz spring for normal keys, and a 3 oz spring for the space bar.

Keyboards

For keyboards built using the modular grid, see Hi-Tek Dovetail Series.

Confirmed

Unconfirmed

The following keyboards are being assumed to be Hi-Tek, but due to lack of Hi-Tek branding, remain unconfirmed:

See also

References

  1. 1.0 1.1 Correspondence with D'Milo Hallerberg and Susan Kennedy, 2017-09-03
  2. Telephone conversation with D'Milo Hallerberg, 2015-08-03
  3. Deskthority — Hi-Tek keyboard
  4. (Wayback Machine) AtariAge Forums — 600/800XL Keyboard variants Archived 2005-06-01.
  5. AtariAge Forums — Hacking the Atari 800 Keyboard & CX85 Keypad onto a USB PC Keyboard Circuit Dated 2009-12-26. Retrievd 2015-07-27.
  6. AtariAge Forms — 800 Restoration Dated 2012-11-24. Retrieved 2015-07-27.
  7. The Dragon Archive — Pippin Last updated 2014-12-06. Retrieved 2015-07-27.
  8. Vintagecomputer.net — Vintage Computer Photos subject: LSI ADM3A Retrieved 2015-07-27.
  9. Deskthority — Volker Craig vc4152
  10. Geekhack — A visit to my local electronics shop Posted 2013-07-05. Retrieved 2015-07-27.
  11. The Vintage Computer Forums — keycaps: NOSCROLL and SETUP keys for DEC VT100 style keyboard Dated 2010-05-22. Retrieved 2015-07-27.
  12. Deskthority — HP2382A terminal keyboard
  13. Geekhack — keyboard switches used in IMSAI IKB-1 from "Wargames" (1983) film Posted 2013-12-17. Retrieved 2015-07-27.