Warning on some Unison UPSes

[Dick Dunn]

mark at intek01.uucp (Mark McWiggins) writes:
> We recently had some power supplies fried by a Unison Unipower 600.
> We had too much of a load plugged into the circuit the UPS was plugged
> into, and instead of doing anything protective or rational like shutting
> itself down, it burned up the power supply on a PC and a modem ...

Can you tell anything about the failure mode?  What did the UPS do that
caused the power supplies to fail?  It seems unlikely that an overload on a
UPS would cause an overvoltage on the output.  I've been trying to
postulate some other sort of failure (in which the nature of the power
supply on the attached device would play some part) - such as clipping in
the UPS output turning into garbage in the power supply.

Is this UPS a sine-wave output type?

> ...Unison is aware of the problem, but I don't know about any
> upgrade/swap policy.

Do they say anything about what to do to avoid it (other than the obvious
"don't overload the UPS":-), or what types of devices would be susceptible?
Is there a danger of damaging components beyond the power supplies in the
attached devices?
-- 
Dick Dunn     rcd at ico.isc.com -or- ico!rcd       Boulder, CO   (303)449-2870
   ...Mr. Natural says, "Use the right tool for the job."