Anything special about converting VAX 11/780 to single phase?

Gunther Schadow wrote: All right. I need to respond to a few assumptions that had been made and of course ask Matt Sell a question. Question first: that shutdown interlock transformer you said is the only thing that really has anything to do with all 3 phases together. Do I have to take any action with this or will it be fine? Comments: the VAX 6000 is really VERY different. It has a power filter box and then a power & logic box and that produces DC current to be distributed to DC regulators. A very involved thing, and that's why the conversion isn't quite so trivial, although the hardest part was to have the guts (and the reserve of spares) trying it. The VAX 11, as the PDP8/A, SA600, and many, many other DEC equipment has just a power distribution box with soandsomany phases in, some switching gizmo, and then panels of standard 110 V plugs labeled 'phase 1', 'phase 2', etc. in either switched or unswitched form. That's all. The only concern I had was about something like this interlock transformer that Matt was talking about. Will I get all my panels powered, the unswitched and the switched ones? About this ground alias neutral wire overload, I think that's just scare without real substance behind it. Given that I have a 25 to 50 A 110 V single phase circuit to devote, my wiring will simply be like this: +--- P1 | ---phase-----------+--- P2 | +--- P3 ---neutral---------+--- N ---ground----------+--- GND since the phase, neutral (and ground, not that it matters) wires are all same gauge, the 30A that go through the phase line come right out of the neutral line. If neutral overloads phase will too. That's what you have circuit breakers and the right gauged wireing for. I can see no risk. The only theoretical risk I could possibly see is that the N line would be underdimensioned internal to the power distribution box. But hey, it's DEC, had big DEC ever built anything under-dimensioned :-). Matt had a different problem, which was he didn't have a 30 or 50 A line to begin with. Finally, there is another thought: I might actually want to use a 220 V 2 phase (4 wires) line that can do 60 A. It's the same line that goes into my computer room in the basement that also runs by my computer room in the garage. I am thinking of just splicing this wire. It's certainly not NEC professional, but it will work and the circuit is overall protected 60 A with big enough wires everywhere and no problem if power fails (only old computers who suddenly stop working.) Is there any problem as far as this interlock transformer is concerned that suggests I not use the 2x110 V (180 degree) line? I would do something like this: ---phase1----------+--- P1 ---phase2----------+--- P2 | +--- P3 ---neutral------------- N ---ground-------------- GND Now, there may be a risk. Remember, when I did this same trick on my 6000 the power would shut down after about 5 minutes run time? It might be a preexisting problem in the PSU, but it might also be that the interlock stuff was being fried because of the 180 degree phase difference i.e. U(P1,P2) being 220 V when it wanted a 120 degree phase difference with a U(Px,Py) = 110 V * 1.5 = 165 V. Any idea what it would do, Matt? thanks -Gunther -- Gunther Schadow, M.D., Ph.D. gschadow(a)regenstrief.org Medical Information Scientist Regenstrief Institute for Health Care Adjunct Assistant Professor Indiana University School of Medicine tel:1(317)630-7960 http://aurora.regenstrief.org