Hi-Tek Series 725 second generation

Hi-Tek Corporation, a division of NMB, produced its 1st generation of PC compatible keyboards primarily as an OEM manufacturer for PC compatible companies such as Tava and Tandon. As it moved on to its 2nd generation of keyboards, more unbranded keyboards were produced which were popular with PC clone manufacturers.

Description

Second generation keyboards use the same basic construction as the 1st generation. This consists of 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 beige, molded plastic with a surface texture created as part of the molding process. The upper case incorporates four screw bosses. The two outer most bosses are used to attach the rear cover. The inner most bosses are used to attach the switch assembly. All four bosses are un-threaded. Self tapping screws to secure the rear cover and switch assembly to the upper case. A set of tabs in the upper case and matching slots in the rear cover provide the primary means of securing the two halves together. The case is assembled by matching up the slots in the rear cover with the tabs in the upper case. Once all tabs have mated with their matching slots, the rear cover slides a few millimeters toward the bottom of the case so that the edge of each slot engages a notch it the matching tab. Two screws are prevent the rear cover from being dislodged thereby disengaging the tabs.

Rear cover

The rear cover is molded from the same plastic as the upper case. A set of slots mate with tabs in the upper case to join the two halves together (described above). The rear cover has two recessed cable ports placed symmetrically to the vertical center line. On XT models, the right port (looking from the top of the keyboard) is marked keyboard, and the left port is marked mouse. A molded protrusion of the rear cover and a matching protrusion in the upper case act as cable retention and mounting location for modular jacks. A pair of feet are separately molded and snap into recesses in the rear cover. The position feet lie flush with surface of the rear cover when retracted and lock into place when extended.

Labels

Most 2nd generation keyboards have a silver serial number label which displays the serial number and a two digit year. Some 2nd generation keyboards have a identification label that lists FCCID, country of origin, manufacturer name and address, certifications and part number. The identification label has a box for serial number if a separate serial number label is not used. All NMB Hi-Tek keyboards were "MADE IN THAILAND". Early models also have the part number label found on some 1st generation AT keyboards.

Cable

Most 2nd generation keyboards have coiled cable with 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. 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 2 screws. The pcb is double sided. The switches are 725 series.

Switches

2nd generation keyboards introduced the first color and 2 eye 725 series switches.

Keycaps

The keycaps are made of PBT with dye-sublimated legends. They have cylindrical tops and sculpted profile.

Styles

There are two styles of 2nd generation keyboards.

XT

The design of the 2nd generation XT style seems to mimic that of the Key Tronic XT keyboards with a raised area above the keys is a raised instead of the "pencil" bar of the IBM. The key layout based on the IBM PC/XT keyboard with a few differences including the orientation of the enter key and swapping of left shift and backslash keys. The layout matches that of the XT Key Tronic. The 2nd generation XT keyboards appear identical from the front to the 1st generation XT keyboards. The PCB is carried over from the 1st generation.

AT

The AT style keyboards had a key layout based on the IBM AT keyboard. The layout is identical to that of the IBM. The case design is also similar to the IBM. Early models lack the status LED panel, instead having the status LEDs integrated into the Num Lock, Scroll Lock and Caps Lock switches and key caps. Later models have a status LED panel very similar to that of the IBM. 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. This PCB is identical to that of the 1st generation AT keyboards. Curiously, despite having the dedicated status LED panel, the 2nd generation AT keyboards continued to use LED switches for the lock keys.

Early model without lock status LED panel

Later model with lock status LED panel
Rear
Right Side
Top
Right Foot
Left Foot
Lock status LED panel
Foot extended
Right cable port
Left cable port
Upper case inside
Internal
Switch Assembly
Rear cover inside

Known XT variants

Serial No	Date	Main Switch	Spacebar Switch	Cable	Branding	Reference
038681	11-85	White 1-Eye Linear	White 1-Eye Linear	RJ-11	None
119316	01-86	Grey 1-Eye Linear	Grey 1-Eye Linear	Black	None

038681

Front with caps
Front without caps
Rear
RJ-11 Connector
Upper case inside - 85-10-02
Rear cover inside - 85-09-25
Main switch
Spacebar switch
Caps Lock switch
Scroll Lock switch
Date Stamp

119316

Front without caps
Rear
Cable port
Main switch
Spacebar switch
Caps Lock switch
Scroll Lock switch

Known AT part numbers

Part Number	Rev	Date	Main Switch	Spacebar Switch	LED Switch	Cable	FCCID	Branding
112083-005	G	12-86	White 1-Eye Linear	Green 1-Eye Linear	White 1-Eye Linear	Beige	AQ659ZAT	None
112980-003		07-87	Grey 2-Eye Linear	Green 1-Eye Linear	Purple 1-Eye Linear	Beige	AQ659ZPC	None
112980-005		02-88	White 2-Eye Linear	Grey 2-Eye Linear	Purple 1-Eye Linear	Beige	AQ659ZAT	None
112980-006		06-87	Brown 1-Eye Tactile	White 1-Eye Linear	Pink 1-Eye Tactile	Beige	AQ659ZAT	None

112083-005

Top view without keycaps
Bottom
Bottom label #1
Bottom label #2
Bottom label #3
Alphas - White 1-eye linear
Spacebar - Green 1-eye linear
Caps Lock - White 1-eye linear with LED
Spacebar stabiliser wire

112980-003

Top view without keycaps
Bottom
Bottom label
Alphas - Grey 2-eye linear
Spacebar - Green 1-eye linear
Caps Lock - Purple 1-eye linear
Num/Scroll Lock - Purple 1-eye linear

112980-005

Overview
Back label
Keycap closeup
Extended foot
Angle view of White switches
Closeup view
Detail of lock switches
Detail of spacebar switch
Stabilisers
Controller IC
Case datestamp 1
Case datestamp 2
One of the 10 hooks keeping together the two halves of the case with the added help of two screws