Re: Inexpensive UPS gotchas with older equipment

From: Bill Gunshannon (bill_at_cs.uofs.edu)
Date: 07/08/05 

Date: 8 Jul 2005 18:12:09 GMT

In article <1120845790.733137.114720@z14g2000cwz.googlegroups.com>,
        jordan@ccs4vms.com writes:
> Recalling a recent UPS discussion here... just had a new experience.
>
> I've got a VS3100-30 sitting on my desk at work; its my main support
> system for local and remote VMS customers so I don't have to use a
> terminal emulator and crappy pc keyboard (which my boss would prefer,
> but thats another issue). It was purchased by the company in 1989-90
> and has been off support since around 1998, but still runs fine.
>
> Our new building is having power issues; line voltage drops to 105 or
> less in the afternoon, and its jittery; its gotten low enough a couple
> times to crash numerous systems, including the VAXstation. Needless to
> say there's no budget for a UPS for my old VAX so I brought a little HP
> 500VA unit that I use for network gear at home (for 2 years, no
> problems). It ran the external drives just fine, so last night I
> recabled power to hook up the VAXstation and monitor.
>
> Within a couple of minutes of powering up, there was a detectable aroma
> of hot electronics coming from the VAX _and_ the VR299 monitor. The
> UPS was not overloaded. After powering off I checked the output
> voltage on the UPS, and it was in line (about 110 at that point, same
> as wall voltage). On battery it measured 116V with a PC and monitor
> (which had no problem) hooked up.
>
> Plugged the VAX and monitor back into the wall, no problem, no aroma.
> So I took a spare 3100 power supply, hooked up a couple of SZ12 load
> resistors to it, and hooked it up to the UPS. Unhappy hot smells
> again. Back to line power, no problem.
>
> I've run an AS200 briefly on these UPS's with no issue, but it appears
> that either the significant seniority or the actual designs of my VAX
> power supplies have made them very unforgiving of simulated sine wave
> power with THD of 38.5% and max single harmonic of 24.9%, or with
> whatever this UPS does to line power when its inline since the smell
> happens either way.
>
> I can't afford a SmartUPS right now, but thats apparently what it will
> take to protect the VAX. Cheapies won't cut it. True sine power all
> the way; I'm a believer. Be careful what you use for your older
> systems. At least my equipment is still running so I guess I caught it
> before too much damage was done.
>

Have you tried it with just the VS3100 and not the monitor? I have
always read that you don't plug monitors or laser printers into those
small UPSes because regardless of what the rating says, they won't
handle it.

bill 

-- 
Bill Gunshannon          |  de-moc-ra-cy (di mok' ra see) n.  Three wolves
bill@cs.scranton.edu     |  and a sheep voting on what's for dinner.
University of Scranton   |
Scranton, Pennsylvania   |         #include <std.disclaimer.h>

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