15 Apr
2001
15 Apr
'01
4:01 p.m.
On Sun, 15 Apr 2001, Richard Erlacher wrote:
Is anbody intimate enough with the VaxStation 2000 to
provide a couple
of details? Here's the deal:
Not really intimate with them, but I have used them to run NetBSD/vax and
Ultrix.
I snagged a VaxStation 2000 box some time back, mainly
for the PSU.
It turns out that it has a couple of lines, on the 9-pin MOLEX main
power output connector, the purpose of which is not clear. There's
one that seems to float at around -6 Volts DC, and another that floats
at high-impedance, yet, when the one at -6 is pulled to 0 (gnd)
through a resistor, the previously floating one suddenly has 9 volts
or so. Do these have a specific purpose that might serve some need
I'm likely to encounter, or are they just for the DEC folks' features?
Is there any way to capitalize on them, or should I just leave them
alone? All I'm after is fairly normal power output, with the added
benefit of a fan and switch. The +5 and bipolar 12's seem to work
fine. Spec's would be handy too, e.g. how much current can be drawn
from each of the supplies and, perhaps from all of them at once?
I think (I'm not positive) this may be related to the nature of the power
supply. I've not actually used them for anything but powering the
components which normally make up a VAXstation 2000. They do have some
interesting qualities, the main one being that they don't work right
unless they've got a load on them.
I've made the mistake of trying to run one diskless--which doesn't work.
As soon as you add a disk drive, then the system goes through it's power
up sequence without problem. DEC did make a diskless version of the
VS2000, but it had a big resistor board that plugged into the internal
drive power cable.
I'm sure someone here can address the actual reasons why the power supply
behaves like this. I think it's a trait of older switching PSUs. But
hopefully my "systems guy" observations provide some useful clues.
-brian.
--- Brian Chase | bdc(a)world.std.com | http://world.std.com/~bdc/ -----
Being an open and honest guy, in the big "Occupation" box in the center
of the sheet, I had written the same thing that's on my business cards.
"Internet Legend". -- K.