Back in the early '80's it wasn't uncommon for switchers to malfunction, or, if
designed somewhat better, to fail to function at all, if no load was present.
This is consistent with DEC's practice of putting out 10-year old technology in
its "current" products. Their rotating memory products were always at least
one, and often three, generations behind the "current" generation in other
makers' products. That ensured maximal profits for DEC shareholders and maximal
bonuses for their execs, though it also ensured last-generation performance or
less for their users.
Dick
----- Original Message -----
From: "Brian Chase" <bdc_at_world.std.com>
To: <classiccmp_at_classiccmp.org>
Sent: Sunday, April 15, 2001 2:01 PM
Subject: Re: VaxStation 2000 PSU info needed
> 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_at_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.
>
>
Received on Sun Apr 15 2001 - 22:03:26 BST