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I own an APC Back-UPS ES 750; it's about 4 years old, and is the only major component remaining in a question that has been boggling me for the last 18 months.

(Yep, I originally posted this question about the possessed desktop, and while I marked a solution and closed the question, a week later the same problem returned)

I've tried plugging the desktop straight into the wall (but left the other components plugged into the UPS) and the desktop still froze. Is it possible that the EM field generated by the UPS is interfering with my desktop components and causing these otherwise-unpredictable system freezes?

To me this sounds like a long shot, but aside from my twin LCD monitors, that just about takes care of all the major components.

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up vote 1 down vote accepted

It is extremely unlikely that a UPS will emit enough EM wave that disturbs operation of a desktop machine - In any event, your average mobile phone emits more radiation than a UPS.

I have reviewed your "possessed desktop" question.

I can see :-

  • Ram out of question
  • Motherboard out of question
  • Display card out of question
  • Cooling out of question

What remains :-

  • Harddrives: sometimes errornous harddrives can result in freezeup for few second, but unlikely to be completely frozen...
  • CPU: in extreme cases the CPU can be faulty - though extremely unlikely - complete freeze can happen where CPU fails intermittently, try superpi/prime95 - does it freeze fast? In this case, try downclocking and slight overvolting the CPU. if this helps then the CPU could be at fault.
  • Power: In some cases the power can be problematic - not the power supply of the PC, rather, the grid supply. if the grid supply is poor, another person starting a engine next door can cause a short brown-out of your grid supply. but UPS should take care of this problem.

Hope that helps.

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I very much appreciate your reading over my initial problem, too. I figured the UPS was a long shot but wanted to ask. As for your other options: I've replaced the hard drive several times, so at this point I'm ruling that out. The CPU is plausible; that was the very first thing I RMA'd when the freezing first began. I downloaded and ran prime95, and the first time I tried it (a few hours ago) the system locked up. Now it's been running over an hour, no problem. As for power, it's had the same issue in two different cities, so I think we can rule out faulty grids, too. – Magsol Jun 7 '10 at 14:59
that said i am very much at lost as with you. though, i would try rebuilding the machine step by step. first, just the power + motherboard + vga card + livecd (ubuntu) and then try some processor intensive use e.g. number crunching... if it works, then these things are ok then add harddrives, redo testing on ubuntu, then install windows 7 to see if changes... and so on and so forth. please do update here your progress. hope i can help you through =) – bubu Jun 7 '10 at 15:35

Long shot indeed - I find it extremely unlikely that a computer that is not faulty would be affected like that even if the UPS does emit much more EM than it is allowed to.

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I figured as much; still wanted to ask, since I'm definitely no electrical engineer. Thanks! – Magsol Jun 7 '10 at 15:00

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