Power for Power Series

[Mark Bradley]

In article <9002070129.AA12557 at physics.phy.duke.edu>, rgb at PHY.DUKE.EDU ("Robert G. Brown") writes:
> I should note that we did try the three phase power (as a physicist, I
> know that the system should NOT be able to see any real difference
> between a hot-neutral pair at 208V and a hot-hot pair at 208V with a
> phase difference -- unless it uses the current-carrying "neutral" as a
> pseudo-ground, which is dumb).  
> 
> When we did it, the machine seemed to boot, but the prom monitor did
> not come up on port 1 (or 2,3 or 4).  We have no graphics monitor, it
> is a server--only configuration at this time.  When we put a scope on
> the backplane and on the serial line itself we got very unusual
> things.  The serial line showed a .15V, 60Hz triangular waveform on
> ALL pins but 1 and 2.  1 had a more attenuated 60Hz signal, and 2 was
> (relatively) quiet.  Obviously this is not at all like what we found
> on a functioning serial line.
> 
> So:  Is our power supply bad?  Is our power bad?  Are any or all of
> the boards bad?  Are the serial ports bad?  Or do we need to "flick
> that little switch over there"?

I replied a bit too quickly, it seems, as I did not address the rest of
your questions.  220, neutral and ground will work too--you're correct
on that one.  As to your triangular waveforms on the serial lines; it
sounds like something is wrong.  Power supply is not likely to be the
problem; there is no switch to flick, to my knowledge; and maybe the
cabling/breakout board for the serial lines has a problem.  The prom
monitor *should* only come up on one port, though, and there may be no
problem at all.  Once the system is up, try `man getty' for info on
your serial ports.

						markb


--
Mark Bradley				"Faster, faster, until the thrill of
I/O Subsystems				 speed overcomes the fear of death."
Silicon Graphics Computer Systems
Mountain View, CA 94039-7311		     ---Hunter S. Thompson

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