Difference between revisions of "BA11-A mounting box"
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Unusually for [[PDP-11]]s, its integral [[power supply]] also provided +12V/-12V [[direct current|DC]], used for the [[MS11-M MOS memory]]'s [[Metal Oxide Semiconductor|MOS]] memory [[integrated circuit|chips]]. | Unusually for [[PDP-11]]s, its integral [[power supply]] also provided +12V/-12V [[direct current|DC]], used for the [[MS11-M MOS memory]]'s [[Metal Oxide Semiconductor|MOS]] memory [[integrated circuit|chips]]. | ||
| − | It came with the [[H7140 Power Supply]], mounted at the rear of the box. There were four main variants, depending on the input [[alternating current|AC]] [[voltage]], and details of the secondary output: | + | It came with the [[H7140 Power Supply]] ([[PDP-11/44]]) or [[H777 Power Supply]] ([[PDP-11/24]]), mounted at the rear of the box. There were four main variants, depending on the input [[alternating current|AC]] [[voltage]], and details of the secondary output: |
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The BA11-A does not use only the standard [[DEC power distribution connectors]]; it also provided special connections on [[bus bar]]s in its power supply, and in some applications (e.g. the -11/44's [[KD11-Z CPU]]), the CPU's [[backplane]] uses unique [[Flexprint cable]]s for power, which go to the special connections (see image). | The BA11-A does not use only the standard [[DEC power distribution connectors]]; it also provided special connections on [[bus bar]]s in its power supply, and in some applications (e.g. the -11/44's [[KD11-Z CPU]]), the CPU's [[backplane]] uses unique [[Flexprint cable]]s for power, which go to the special connections (see image). | ||
| − | For backplanes which did not have the Flexprint cables (e.g. that of the -11/24's CPU), a special 'Power Distribution Board' ([[DEC part number]] 54-13815) mounts to the bus bars and provides the needed connectors. | + | For backplanes which did not have the Flexprint cables (e.g. that of the -11/24's CPU), including the [[DD11-DK]], [[DD11-CK]], [[RK11-D]], etc., a special 'Power Distribution Board' ([[DEC part number]] 54-13815 for the 11/24 or 54-13632 for the 11/44) mounts to the bus bars and provides the needed Molex connectors. |
==External links== | ==External links== | ||
Revision as of 17:08, 19 December 2025
The BA11-A mounting box is a 10-1/2" mounting box; the terminal variant letter notwithstanding, it is just about the last in the line of BA11 mounting boxes. It was introduced with the PDP-11/44, and was also used with the PDP-11/24 and VAX-11/730.
Unusually for PDP-11s, its integral power supply also provided +12V/-12V DC, used for the MS11-M MOS memory's MOS memory chips.
It came with the H7140 Power Supply (PDP-11/44) or H777 Power Supply (PDP-11/24), mounted at the rear of the box. There were four main variants, depending on the input AC voltage, and details of the secondary output:
| Model | Input | Memory voltages |
|---|---|---|
| -AA | 115 | +12V, -12V |
| -AB | 230 | +12V, -12V |
| -DA | 115 | +12V, -15V |
| -DB | 230 | +12V, -15V |
Maximum power was 1350W with maximum load applied; it could provide 120A of +5V, and 10A of memory refresh +5V power to MOS memory; 3A of +15V, 3A of -15V; and 5A of +12V, 1A of -12V or -15V.
The H7750 Battery Backup Unit, which provided refresh power during brief power outages to MOS memory mounted in the BA11-A, was an option.
Power connections
The BA11-A does not use only the standard DEC power distribution connectors; it also provided special connections on bus bars in its power supply, and in some applications (e.g. the -11/44's KD11-Z CPU), the CPU's backplane uses unique Flexprint cables for power, which go to the special connections (see image).
For backplanes which did not have the Flexprint cables (e.g. that of the -11/24's CPU), including the DD11-DK, DD11-CK, RK11-D, etc., a special 'Power Distribution Board' (DEC part number 54-13815 for the 11/24 or 54-13632 for the 11/44) mounts to the bus bars and provides the needed Molex connectors.
External links
- BA11-A Mounting Box and Power System Technical Manual (EK-BA11A-TM-003)
- BA11-A Field Maintenance Print Set (MP00832 - May '79)
- BA11-A Field Maintenance Print Set (MP00832 - Apr '87)
- Repairing a H7140 power supply - informative blog entry on repairing an H7140 power supply
- Fan Overhaul BA11-A
