View source for H742 Power Supply

The '''H742 Power Supply''' is a modular [[power supply]] system from [[Digital Equipment Corporation|DEC]], used in [[PDP-11/40]], [[PDP-11/45]] and [[PDP-11/70]] systems mounted in a [[BA11-F Mounting Box]].

It runs off standard wall [[Alternating current|AC]]; it can be [[jumper]]ed to use either 110V or 220V supply.

The H742 supplies a modest amount of +15V [[Direct current|DC]] power to various [[backplane]]s mounted in the BA11-F, along with a [[line time clock]] signal, and AC and DC 'power OK' signals.

It also supplies 20-30V AC to several [[DEC standard modular regulators]] (up to five, in spaces numbered 'A' through 'E') mounted in the H742, which provide other voltages such as +5V to the backplanes in the mounting box.

Generally the [[power harness]] supports only limited options as to which regulator can be in which spaces; e.g. the later -11/40 harness mandates that A, B and C hold [[H744 +5V Regulator]]s, D holds an [[H745 -15V Regulator]], and E may hold either an H745 or [[H754 +20V, -5V Regulator]].

The harness used [[DEC power distribution connectors]] to provide power to the backplanes; it normally used the [[DEC standard power wire colour coding]].

The H742 did not support the [[Remote Switching Control Bus]]; the H742 was generally plugged into an [[861 Power Controller]], which did have the remote control capability.

Later versions of the basic H742 are the H742A and H7420A; the differences are not yet known.

==See also==

* [[H765 Power System ]]

[[Category: DEC Hardware]]