<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0//EN" "http://www.w3.org/TR/REC-html40/strict.dtd"> <html><head><meta name="qrichtext" content="1" /><style type="text/css"> p, li { white-space: pre-wrap; } </style></head><body style=" font-family:'Sans Serif'; font-size:9pt; font-weight:400; font-style:normal;"> On Monday 23 July 2012 09:59:03 Tom Schouten wrote: > Any ideas what this might be? Is this a known property of these cheap > square-wave approximate sinusoid boxes? Hi, Tom... That would be my guess, but I fully admit that I don't really know. I've been using my original APC "BackUPS Pro 650" for over 13 years now on my primary PC and never had a problem with it in all that time (and through many power failures and other smaller powerline "glitches", like when an incandescent lightbulb blows out and momentarily freaks out the powerline, causing the UPS to momentarily take over). But this is a (relatively) big, rather heavy, pure sine-wave unit and cost $258 back then (Jan 1999). I suspect the lighter, cheaper units that seem to have proliferated these days just aren't as capable (e.g. square wave instead of pure sine wave), although I do successfully use one like that (an APC 'BackUPS 350' [Model: BE350R], $30 in Oct 2007) as a backup to my DVR so that it doesn't lose programming on a power loss. That cheap UPS works fine for that limited purpose. A little Google activity yielded this comment in an Amazon review: "When I called APC tech support to find out why my new BX1000G* would not power my Dell XPS 9000 in a power outage, the customer rep knew exactly what was wrong. My Dell computer (and many others) needed a pure sine wave input and this APC series of UPS produces a "step approximated sine wave". She even emailed me a company white paper that explained why it was not compatible with many of the newer energy star compliant computers that have "Active Power Factor Correction" power supplies. She recommended that I exchange it for their "smart-ups" model SMT1000 which produces a pure sine wave. This sounded OK until I discovered that the SMT1000 costs almost four times as much as the BX1000G! Google for "apc ups active pfc" to learn much more about this problem." There's more to that person's review that you may find useful. He went with a CyberPower CP1500PFCLCD instead of the <a name="bxgy_x_title"></a>APC BR1000G and seemed happy with that. Hope this is useful.... Regards, Bill </body></html>