Subject: Re: VAX7000 3-phase
To: None <port-vax@NetBSD.ORG>
From: Eric Smith <>
List: port-vax
Date: 03/04/2002 22:48:55
John Wilson wrote:
> Not to fan the flames but:  in the DEC-2065 power supply, there really
> honestly IS a three-phase transformer followed by a six-diode bridge
> rectifier, for at least one of the weird ECL voltages [...].  I guess
> they really cared about ripple...

You can view a three-phase transformer as three separate transformers,
each on a different phase of the three-phase.

The ripple out of a three-phase bridge is *much* less than out of a
full-wave bridge on a single phase, so not as much capacitance is
needed to filter it.

In the KL10, the first stage of the ECL power supply uses the
three-phase transformer, three-phase bridge, and a bank of capacitors
to produce -12V at 490A max.  Then they used ten LINEAR regulators
at -5.2V 35A each for the ECL power supplies, and four at -2.0V 35A
each for the ECL terminations.  They're burning up 2/3 of the power
in the linear power supplies.

Nothing else in the KL10 needs three-phase.  Everything else runs from
a single phase, including all of the non-ECL electronics, the PDP-11/40
front end, and the blowers.