Hi-Tek Series 725 first generation

In 1984, Hi-Tek Corporation, a division of NMB, began production of a line of PC compatible keyboards using it's newly designed "low profile" 725 switch. This line of keyboards would be the first in several generations of PC keyboards to feature this switch.

Description

First generation keyboards have 4 major components, the upper case, the switch assembly, the rear cover and the cable.

Upper case

The upper case is a single piece of thick, molded plastic with a beige, textured coating. The base plastic is white with a slightly yellow tint. The case has 8 threaded bosses. The bosses at the top and bottom of the case are use to attach the rear cover. The 4 shorter bosses on the sides of the case are used to attach the switch assembly. Early models had threaded brass inserts while later models had the screws threaded directly into the plastic. The top edge of the case features a series of half round protrusions that may be for strengthening. A single cable port is located about a quarter of the way in from the right hand side of the case. The feet are black plastic. A pigtail like spring holds each foot in place and supports two positions.

Rear cover

The rear cover is essentially flat with a "V" shaped trough that runs the laterally a few centimeters below the top edge. The cover is black. Early models have rear covers made of painted steel while some later models feature molded black plastic with a slight texture. The early models also have a pair of grounding screws which are not present on later models.

Markings

A 4 digit date code is stamped in white paint on the rear cover. The format of the date code is MMYY. Most also have a 5 or 6 digit serial number sticker affixed to the rear cover. Later models may have a part number sticker listing part number, revision and code. At least on example has a "Made in Taiwan" sticker.

Cable

The coiled cable is approximate 1 meter long and stretches up to 2 meters comfortably. It has a molded DIN 5-180 connector on the PC end and a 6 pin header on the PCB end. A rectangular block is molded onto the cable where it exits the case. This block fits into a molded boss in the upper case that provides retention to prevent the cable movement. Cables in both black and white/beige and known to exist. Early cables have 5 conductors and a separate protective ground lead which attached to on of the screws that connect the rear cover to the upper case. Later cables have 6 conductors but lack the ground lead. Later cables are also thicker than earlier cables and have a larger diameter coil. Some models replaced the cable with a RJ-11 modular jack which mounted in the same location as the cable.

Switch assembly

The switch assembly consists of the PCB, switches, key caps and switch plate. The switch plate is constructed of stamped steel with a thin, painted finish. The ends of the plate are bent to mount to the upper case using 4 screws. The pcb is double sided. The switches are 725 series. Later models switched from a Toshiba microcontroller to Mitsubishi.

Switches

First generation keyboards used white, one eye, linear switches. There were two variants. Early keyboards used the very first 725 series switch, often referred to as the "Gundam" switch due to its similarity to the head of a Gundam from Japanese anime. Gundam switches are distinguished by the curved contact opening. Later keyboards used the more common variant with a rectangular contact opening and square eye.

• 

  Gundam

• 

  Common one-eye

Keycaps

The keycaps are made of PBT with dye-sublimated legends. They have cylindrical tops and sculpted profile. Early XT versions used an ABS spacebar as is evidenced by yellowing. Later models and future generations used a PBT spacebar.

Styles

There are two styles of first generation keyboards.

XT

The XT style keyboards had a key layout based on the IBM PC/XT keyboard. Differences include the orientation of the enter key and swapping of left shift and backslash keys. The design seems to mimic that of the Key Tronic XT keyboards using a raised section above the keys instead of the bar of the IBM. The Key Tronic key layout was also the same.

• Early Model
• 

  Front

• 

  Rear

• 

  Side View

• 

  Internal

• 

  Switch Assembly

• 

  Inside of Upper Case

• 

  PCB

• Tandon Model
• 

  Front

• 

  Rear

• 

  Internal

Note: The Tandon model combines the later style cable with the earlier metal rear cover. In place of ground lead, rear cover is grounded through PCB to the switch plate using a screw (see rear view).

AT

The AT style keyboards had a key layout based on the IBM AT keyboard. The layout is copied exactly from the IBM. The case design is also similar to the IBM but lacks the status LED panel. The status LEDs are integrated into the Num Lock, Scroll Lock and Caps Lock switches and key caps. The AT uses a different PCB design than XT. The PCB also feature anti-ghosting diodes which provides N-key rollover. A large screw near the space bar switch grounds the PCB to the switch plate.

• 

  Front

• 

  Rear

• 

  Side

• 

  Internal

• 

  Switch Assembly

• 

  Inside of Upper Case

• 

  PCB

• 

  Status LED switches

Known examples

Style	Date	Switch	Rear Cover	Cable	Branding	Reference
XT	11-83	Gundam	Metal	Black Early	TAVA PC
XT	08-84	Gundam	Metal	Black Early	TAVA
XT	10-84	Gundam	Plastic	RJ-11	None
XT	12-85	Common	Metal	White Later	Tandon
AT	11-85	Common	Plastic	Black Later	None