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Univac A series boards (general description)

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The Univac 1040 (small) and 1050 (medium size) computers are composed of boards of the A family. These boards are short (12.6 cm), and are the predecessor of the B-family. The latter boards are somewhat longer (16.2 cm) and can therefore carry more electronics. In terms of connections and type of electrical circuits the A and B series boards are identical, and they can be mixed if you remove the plastic standoff that is only found on the A series, although that was not done by Univac. The A boards have design dates ranging from 1962 to 1964.

The boards contain circuits made out discrete germanium switching transistors and diodes (DTL logic). The circuit board technology is advanced: double sided with plated through holes. Power is supplied through one side of the connector (9 pins), while the logic connections are on the other side (18 pins). Power supplies are -30 V (primary power), -8 V (used for clamping the output to increase speed), and -20 V (used to provide a negative bias to the basis of he switching transistor, to cancel the voltage drop over the input diodes).

Typical circuits are NOR gates, AND gates (diodes only), and flip-flops with delayed outputs. The entire 1040 system consists of 8 racks with 125 boards each (5 rows of 25 boards). The rack has prewired connections to all pins providing power, and the boards are connected using wire-wrap technology.

The memory of the 1040 system is core memory: ranging from 4k x 6 bits (+ 1 bit parity) to 16 k x 6 bits. The 1040 computer is built out of 53 different types of board, where many are specialized to functions such as driving core memory and reading sensors. In my collection I have complete schematics and 23 types of actual boards (mostly logic functions). The small size of the boards make their functions simple: a few gates and/or one flip-flop. More complex circuitry is built by combining multiple boards.

 A typical board is shown here, as well as the inside of a 1050 system (note the standoffs visible right of the person).

Univac A8 board

 inside look into a 1050 system


Last Updated on Tuesday, 30 December 2008 20:21