Curiosity about power supplies (BA11)

Wolfe, Julian wrote: Certainly possible, with either OTS PC style or switcher PS modules. For the 'classic' DEC brick-style regulator modules as in the BA11-K box: H744 ....... +5V @ 25A H7441 ...... +5V @ 32A (upgrade to the H744) H745 ...... -15V @ 10A H754 ...... +20V @ 8A & -5V @ 1-8A 54-11086 .. +15V @ 4A A standard BA11-K box has 2xH744 (or later 2xH7441), 1xH745, 1x54-11086, and usually a spot for 1xH754 (for core memory, not req'd if no core). Each of the backplanes (DD11-D/C) has one or two AMP MateNLok connectors that handle the power distribution to the various slots, typically a pair of 14ga wires for +5V, and one wire each for the other voltages. Each 9slot SU is nominally 10-15A max at +5V, easily handled by a small switcher. The main problem I see with OTS PC supplies is they are +12V and not +15V. Older DEC cards expect +15V input and do on-board regulation to +12V. Only some of the later MOS memory cards (like MS11-PB 1MB for the 11/44) expect +12V on the backplane (which is supplied directly from the BA11-A supply). I have built a benchtop debug station that uses a DD11-CK 4 slot SU with an inexpensive +5V at 10A, +15V at 2A, -15V at -2A modular supply. I suppose it would be fairly straightforward to rip out the rear end of a BA11-K box an lineup 5 or 6 of these and completely replace the power subsystem. For the BA11-K box remember the fans not only cool the boards but also the power regulators and internal power supply transformer. I would not disable one of the fans even if the box were lightly populated. Power supplies want to be in a cool environment, heat is your biggest enemy (besides time, I guess).