H777 Power Supply
The H777 Power Supply is the power supply unit for the BA11-L mounting box from DEC. It provided DC current at voltages of +5V, +15V and -15V, with optional +20V/-5V for use with core memory. A later variant (used for the PDP-11/24 in the BA11-L box) also provided +15V/-15V for use by its RS232 asynchronous serial lines.
An optional H775A Battery Backup Unit allowed provision of power to MOS main memory units mounted in the BA11-L, allowing their contents to be retained during brief power outages.
A combination of up to 3 modules, composed of boards with integral heat sinks, provided different combinations of output voltages:
- +5V Regulator - DEC part number 70-11073 or 70-12909 (all configurations had to include one of these)
- MOS Regulator, +/- 15V, +5VB - 54-11601
- Core Regulator, +20V, -5V - 54-11599
There are a large number of different models of the H777, but they boil down to a combination of three (later four) options:
- 110V or 220V AC input
- The optional +20V/-5V core supply
- An upgraded +5V power supply (70-12909) which produced 32 amps instead of the 25A of the original (70-11073)
The fourth option is the 'communication regulator', 54-13764, which provides +15V/-15V.
The models are:
|-AA||115||25A +5V, MOS and core|
|-AB||230||25A +5V, MOS and core|
|-BA||115||25A +5V, MOS only|
|-BB||230||25A +5V, MOS only|
|-CA||115||32A +5V, MOS and core|
|-CB||230||32A +5V, MOS and core|
|-DA||115||32A +5V, MOS only|
|-DB||230||32A +5V, MOS only|
|-UA||115||32A +5V, MOS, communication|
|-UB||230||32A +5V, MOS, communication|
The H777 does not use a power harness; rather, it has a 'power distribution board' built into one end panel, 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.
- BA11-L mounting box technical manual (EK-BA11L-TM-001) - the H777 is covered on pp. 14-19 and Chapter 3, pp. 36-80
- PDP-11/24 System Technical Manual - covers the communication regulator in Appendix A
- 11/04 Engineering Drawings - H777-0 Vol. 1 Field Maintenance Print Set (MP00016) is on pp. 104-142
- 11/24 Field Maintenance Print Set - H777-0 Vol. 2 Field Maintenance Print Set (MP00309) is on pp. 169-194