A Thought... The filter may not be able to carry the full load on
one or two inputs. You might need to connect a single phase up to
two (or more) inputs...

clint

On Tue, 24 Apr 2001, Robert F Schaefer wrote:

> Well, after another look in the beasties guts, converting it to run on
> single phase 220 should be a simple task.  What I will do to mine is
> remove the large three-phase cord (DEC #17-01806-01) and substitute a
> home-brew cord #12-4 SO with a NEMA L16-20P plug.  
> 
> A few more details:
> 
> H405-E power distribution box, US 240 volt single phase (dryer or range
> type).  There are three receptacles on the box, two on the back (where the
> cord comes in), labeled FL3, & FL4.  These are switched, filtered power,
> connected to the A phase (FL3) and B phase (FL4), fused immediately
> adjacent to each receptacle. As I plan to feed the A phase and and B phase
> with the two hot legs from the 240 volt power, nothing needs to be done
> with these.  The third receptacle, J5, is located on the back side of the
> box, internal to the chassis.  This is fed from the C phase.  As it is
> internal to the computer, there is a good bet that something needs to be
> plugged in there, so it will need to be moved to either the A phase or B
> phase.  This is most easily accomplished by opening the box, loosening the
> nut holding the brown wire going to the receptacle, and moving it to either
> the red wire (A phase), or yellow wire (B phase).  I'm gonna put it on the
> A phase, Just Because.  There are a number of other connections on the box,
> these don't interest us at this time, with one exception: J4 on the back just
> above where the cord enters.  This is protected/covered by a metal
> shield-- DO NOT REMOVE THIS COVER!  Under this metal plate is a plug that has
> UNSWITCHED (as in energised whenever the VAX is plugged in) three phase
> power.  Anything that needs this plug will need to be examined, to see if
> it will operate properly with 240 volt single phase, instead of the 208
> volt three phase it's expecting.
> 
> There is one other safety modification that IMHO should be performed. 
> Inside the `Power & Logic Box'-- the 300 volt DC power supply-- there are
> three fuses just before the the power enters a full wave bridge rectifier
> (the black thing on the B-I-G heatsink)  The fuse to the unused phase
> should be removed. This will prevent power from backfeeding should the
> rectifier fail in a shorted mode.  This is particularly advised for anyone
> who will be leaving the original cord on (Brian ;) -- one pin of the plug
> could become energised!
> 
> Now, the fine print:  I haven't exactly *done* this yet.  It is what I
> will be doing, but I have other, more pressing, projects that are
> consuming most of my time at the moment.
> 
> And please don't hurt yourself!
> 
> ja ne
> 
> Bob
> 
> 
> 
>