DEC use of switching supplies (Was: Looking for VAX6000 items)

Noel Chiappa jnc at
Wed Jul 14 12:55:45 CDT 2021

    > From: Chris Zach

    > The older Vaxes had linear power supplies if I recall up to the time
    > of the Decsystem/2020 (when they went switching at last)

Really? The H742 power supply:

(well, technically, the associated 'bricks', such as the H744, etc) from
about 1972 were switching supplies, so I'm suprised that the much later
VAXen (any of them) used linear supplies.

Of course, the H744/etc switching supplies didn't use a lot of the techniques
used in modern switching supplies to make them small and light (e.g. stepping
up the frequency to allow use of a small transformer); the H742 still has a
whacking great transformer in it. But they were switching supplies (as we
discussed here a while back at some length), not linear.


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