Pure Sine Wave UPSes for New Dell PCs
in [Dell]
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From: William R. Walsh on 9 Apr 2010 10:15 Hi! > Not necessarily. The PS in the 9000 is rated for 475 Watts and > puts out a true 475 Watts. That's not quite what I'm getting at. How well filtered is the input for the supply? How well will it continue to operate under stressful conditions (like a low line voltage)? Meeting the published specifications for output is just one of many criteria. And while most of Dell's power supplies are of good quality, a comparison to something like a PC Power and Cooling unit would make them look cheap and maybe even a little flimsy. Given that Bestec supplies are showing up in some low end Dell boxen, I'd not be surprised to learn that even the higher end machines are having quality cutbacks here. > I've seen some name brand supplies put out less > than their rating. Sure. And there are always dishonest no-name makers to worry about as well: http://greyghost.mooo.com/psuthoughts/ That's the first of two that I've seen. After finding another one (in another eMachines computer), I see that whoever made it did do some re- engineering, mostly accomplished by adding more metal to the heatsinks. I guess they hoped this would make the supply live a little bit longer. The second one wouldn't even produce enough power to let the machine operate correctly, and I'd bet it wasn't pushing a load of more than perhaps 80-100 watts across all of its outputs. All problems disappeared upon replacement of the power supply with an honestly specified AGI 350 watt unit. The owner claimed that no one except Best Buy had ever serviced the machine. I don't have a high opinion of their service operations, but I'd hope that they would at least use decent quality, honestly specified replacement parts. William
From: William R. Walsh on 9 Apr 2010 10:17 Hi! > That's not necessarily because my UPS doesn't produce a > sine waveform. Actually, it sounds like it's because you turned it off. :-) > For one thing, at 550 VA, my UPS is way under-powered. You should get a bigger one. An overloaded UPS won't always take it gracefully. I've seen overloaded UPS units go off with a bang, especially the cheaper ones. > For another, this sissy little UPS probably doesn't have a > fast enough transfer time. The power supply filter caps should bypass that problem, as they usually hold enough energy to see the power supply past little dips and sags. They only manage to hold about a second or so's worth of energy most of the time. William
From: Daddy on 9 Apr 2010 10:22 William R. Walsh wrote: > Hi! > >> Not necessarily. The PS in the 9000 is rated for 475 Watts and >> puts out a true 475 Watts. > > That's not quite what I'm getting at. How well filtered is the input > for the supply? How well will it continue to operate under stressful > conditions (like a low line voltage)? > > Meeting the published specifications for output is just one of many > criteria. And while most of Dell's power supplies are of good quality, > a comparison to something like a PC Power and Cooling unit would make > them look cheap and maybe even a little flimsy. Given that Bestec > supplies are showing up in some low end Dell boxen, I'd not be > surprised to learn that even the higher end machines are having > quality cutbacks here. > >> I've seen some name brand supplies put out less >> than their rating. > > Sure. And there are always dishonest no-name makers to worry about as > well: > > http://greyghost.mooo.com/psuthoughts/ > > That's the first of two that I've seen. After finding another one (in > another eMachines computer), I see that whoever made it did do some re- > engineering, mostly accomplished by adding more metal to the > heatsinks. I guess they hoped this would make the supply live a little > bit longer. > > The second one wouldn't even produce enough power to let the machine > operate correctly, and I'd bet it wasn't pushing a load of more than > perhaps 80-100 watts across all of its outputs. > > All problems disappeared upon replacement of the power supply with an > honestly specified AGI 350 watt unit. The owner claimed that no one > except Best Buy had ever serviced the machine. I don't have a high > opinion of their service operations, but I'd hope that they would at > least use decent quality, honestly specified replacement parts. > > William This gives me an opportunity to ask this question: Since the 9000 has a PFC power supply - even though a Dell tech support rep assured me that "no Dell computer have PFC supply" - does that mean that its 475 watt power supply really delivers a maximum of 475 watts? Daddy
From: RnR on 9 Apr 2010 10:28 On Fri, 09 Apr 2010 00:31:04 -0400, Daddy <daddy(a)invalid.invalid> wrote: >Tom Lake wrote: >>> I maintain that Dell is cheapskating on the quality of their power >>> supplies, and they may have a nasty backlash from doing so. (But then >>> again, I'm a pretty big believer in "do it right the first time" for >>> stuff like this.) >> >> Not necessarily. The PS in the 9000 is rated for 475 Watts and puts out >> a true 475 Watts. I've seen some name brand supplies put out less than >> their rating. >> >> Tom L > >Well, I conducted my little experiment...pressed the power button on my >UPS to turn it off, and...my computer and monitor immediately shut off. > I assume the UPS battery is not dead ???? >That's not necessarily because my UPS doesn't produce a sine waveform. >For one thing, at 550 VA, my UPS is way under-powered. For another, this >sissy little UPS probably doesn't have a fast enough transfer time. > >By the way, don't waste your time asking Dell technical support about >power supplies or UPSes. They don't have a clue. > Thanks for the info but heck, I'd be just happy if I could understand their English when i've called them (admittedly a couple of years ago) much less about UPSs.
From: William R. Walsh on 9 Apr 2010 10:34
Hi! > does that mean that its 475 watt power supply really delivers > a maximum of 475 watts? That's not what PFC does. PFC tries to compensate for the fact that the components inside a power supply (particularly the capacitors and inductors) may mess up the relationship of voltage to current in an AC power waveform. In other words, your computer's power supply may be "polluting" the power line. With resistive loads (like heaters and such) the voltage and current are in perfect synchronization with one another, giving these devices a power factor of "1". Depending upon how it is loaded, the power factor of your PC's power supply can change. A passive PFC circuit performs a fixed amount of power factor correction and does not adapt to differing load conditions. Active PFC works by adjusting the level of power factor correction based on how hard the power supply is working. The idea is to get things as close as is possible to a power factor of 1 (the perfect value). Whether your power supply will meet its listed output is another matter entirely. The ratings of each major component--the switching transistors, rectifiers, transformers, capacitors and other stuff-- must be considered. There must also be sufficient cooling for these parts, especially the rectifiers and switching transistors. Otherwise they will go "boom". See my other posting for a comparison of two other power supplies, one of them dishonestly specified. You can easily see how the honestly specified supply has much better build quality--it can more easily dissipate heat and the major components are larger, serving as a rough indicator that they are capable of more work. William |