Stupid AC wiring question (220-ish Volts...)

Jacob Ritorto jacob.ritorto at
Thu Feb 5 21:59:04 CST 2015

  What you're describing seems perfect to me, power-wise.  I use that sort
of 220 setup for arc welders and such.

( ### Before trying test below, keep one hand in pocket if you're new at
this - don't risk getting one leg of mains power through each hand and
across your heart, which can make it stop ### )

    When you put your meter across the two hot wires, do you get something
in the 220 to 240 AC volts range?  If yes (obviously dryer wouldn't run,
otherwise), you're good and that would pretty much be your answer.  For
extra safety, plug the meter probes in with the breaker off, then turn
breaker on and read it so you don't ever have to touch anything dangerous.

  If you're reading 220-240 and you want to go forward with testing the
computer, I guess the lack of chassis grounding you're describing could be
an annoyance, but if you have good old steel pipe for your water service,
you could just ground the chassis to that with a clamp for a quick power-up

 Then if your machine's ok, get the electrician in there and have it set up
to code.

  Since I'm not an electrician, I'd wait for a little more corroboration
than just my $0.02, though.  My level of training is "back-yard" at best.


On Thu, Feb 5, 2015 at 10:28 PM, Josh Dersch <derschjo at> wrote:

> I picked up a "large" machine* (for certain definitions of large) that's
> currently configured for 220-240V; my house at the moment lacks 220V
> receptacles.  I was already planning to get an electrician out here to put
> in some beefier wiring at some point (I have a couple of machines that draw
> 15-20A off of 120V that I'd like to be able to run) but I wasn't yet
> planning on doing 220V unless I have to.
> (It looks like in theory it's possible to reconfigure the supply for 120V
> but I lack the docs to do so with any level of confidence...)
> I don't know if this machine works, and I'd rather not invest in 220V
> wiring quite yet unless it does.  And, let's face it, I'm spoiled and I
> demand instant gratification and I'd like to know as soon as possible if
> this machine is a basket case or not.
> So:  since all this stuff is in the basement, I'm just about 15 feet away
> from the dryer, which at first glance runs off an outlet that meets my
> needs.  I even have a NEMA 10-30p plug here that I could wire up to the
> existing power cable for the computer.  But looking into it I have doubts
> that it's actually that simple; in particular since this house was built
> well before 1996 and so the outlet is not grounded; there's a neutral lug
> and two hot lugs (I assume two 120V A/C lines out of phase?) and I'm
> guessing that might not sit well with the power supply in this computer.
> But then, I'm a rank amateur when it comes to house wiring and A/C and
> power supplies and all of that so I thought I'd ask the cctalk collective
> whether this can be made to work or if I should simply wait for a
> professional to take care of it...
> Thanks as always,
> Josh
> * An AMT DAP 610, if you must ask.  It's an array processor from the late
> 80s, with 64x64 1-bit processors.  If the machine doesn't run I'm pretty
> much SOL for spare parts, schematics, service manuals, or anything beyond
> customer-level documentation (which I've recently scanned, btw, if anyone's
> curious...)

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