-----Original Message-----
From: Brian D Chase <bdc@world.std.com>
To: NetBSD/vax Mailing List <port-vax@netbsd.org>
Date: Tuesday, 26 May 1998 12:10
Subject: VS2000 PS quirk? [Was Re: Anyone running on VS2000 w/small memory?]


>
>Can anybody more familiar with VS2000s or maybe even electrical power
>systems shed some light on perhaps why a VS2000 would need a load on the
>drive power connectors to operate normally?


Switch mode power supplies usually require a load to function correctly.  I
have seen standard PC supplies in perfect order refuse to deliver correct
voltage (when measured with a DMM) under no load conditions.  Hanging a
motherboard or disk drive onto the supply seems to make it work properly.
In this case I would have expected the motherboard to provide sufficient
ballast to run it.  I have noted that supposed "diskless" vaxstations
usually have a small drive that is used as a local swap when running vms
booted from a cluster.  Another possibility is that the power supply in the
vs2000 is a bit tired, and is putting noise on the supply rail under low
load.  Best fix for that is to replace all the electrolytic capacitors in
the supply.  They tend to dry out in time, which is accelerated if they are
near hot things, like regulator or switching transistors in psu's.

Hope this helps.


Geoff Roberts
Computer Systems Manager
Saint Marks College
Port Pirie  South Australia.
My ICQ# is 1970476
Ph.  61-411-623-978 (Mobile)
       61-8-8633-0619 (Home)
       61-8-8633-0104 (Fax)