BA11-M mounting box

The BA11-M mounting box was the first QBUS PDP-11 mounting box from DEC. It included an H780 power supply (which provided 18A of +5V, and 3.5A of +12V); and an H9270-A 4-slot Q/Q backplane, which could hold quad-sized cards.

In the beginning the BA11-M was for PDP-11/03's, but the LSI-11 used in that machine was only Q16 capable, making the Q18 H9270-A backplane somewhat excessive. Later on it was used for the Q18/Q22 PDP-11/23/PDP-11/23+, too.

It was available both with a front panel with a bezel (with 'Power On', 'Run/Halt' and 'LTC On' switches, and power and run status indicators); and also with a blank front panel (for use as an expansion box).

The backplane was mounted vertically, facing forward; the front panel could be removed for card insertion/removal. The power supply was mounted longitudinally, beside the card array. Cooling fans mounted in the side of the power supply passed air both over the boards, and through the power supply.

It was a 3-1/2" tall mounting box; its other dimensions were 17-1/2" wide (19" for the front panel), and 13-1/2" deep. The rack mounting was 15" long. It weighed 40 lbs (without any boards).

The BA11-M was replaced by the BA23 Enclosure from 1983 onwards.

External links

• microcomputer interfaces handbook - the BA11-M is covered on pp. 67-73 (pp. 75-81 of the PDF)