H777 Power Supply

From Computer History Wiki
Jump to: navigation, search

The H777 Power Supply is the power supply unit for the BA11-L mounting box from DEC. It provided DC current at voltages of +5, +15 and -15V, with optional +20V/-5V for use with core memory.

There are a large number of different versions, but they boil down to a combination of three (later four) options:

  • 110V or 220V AC input
  • The optional +20V/-5V supply
  • An upgraded +5V power supply (7012909) which produced 32 amps instead of the 25A of the original (7011073)

The fourth option (used in the PDP-11/24 in the BA11-L box) provided +12V/-12V for use by its MS11-M MOS memory instead of the +15V/-15V.

It does not use a power harness; rather, it has a 'power distribution board' which holds the usual DEC power distribution connectors; the backplane(s) mounted in the BA11-L plug in there.

The power distribution board also holds a connector for the usual DEC Remote Switching Control Bus; this could be used either as an output (on boxes which contained a front panel) or an input (for boxes used as expansion boxes).

It was mounted longitudinally, at one side of mounting box, and included its own cooling fan.