> 2) IFF the 110vac power supplies can be separated
>    and IFF they are isolated via isolation type
>    transformers (simple 110x110 things at the
>    required current load), then you ought to be
>    able to separate out each power supply and
>    run them on a single phase power with all
>    power supplies paralelled in inputs to one
>    110v 30 amp circuit (marginal, but ought to
>    work and supply enough power).  Separate to
>    3 circuits, if needed.  Check the supplies,
>    since I don't remember offhand if they did
>    or did not have input isolation transformers
>    already built into the input circuits.

I doubt that they have "input isolation transformers" per se,
but they're switching power supplies made for use on AC mains
power, so the outputs are isolated from the inputs.  That's all
that's required.  The power supplies should be perfectly happy
to all run on 120V on the same phase, since they don't have any
way to "know" that the other supplies aren't on different phases.

The thing you've got to watch out for is any other stuff attached
to the three-phase power input.  A few DEC systems used three-phase
fans.  And some of DEC's three-phase power controls would shut down
if a phase was missing.  As long as you bypass the power control
(don't have either its inputs or outputs connected), you should be
OK.

However, I've never been close to a 7000, or seen any of its
documentation, so this is only based on my experiences with other
DEC machines.