Dave,

I had problem with my XPS 435T on an APC BackUPS.  When I turned on a vaccum plugged in to the same circuit the syetm would power off, eve though the UPS was hooked up and never switched to battery.  I purchased an APC Smart UPS 800 and have not had the same issue since.  So, in my experience, you'll want to go with the Smart UPS or something similar.

Thanks Spart. This gives me something to compare to. I'll check out the 800. I appreciate your reply!

First, is the power supply on the 435T a power-factor correcting supply, and second, should I be concerned about connecting a stepped approximation sine wave UPS to this computer? The UPS that I'm considering is the CyberPower CP1500AVRLCD.

I'm not sure about the answer to the first question, but I have an anecdotal answer to the second. My XPS 435T does not seem to work with my APC Back-UPS XS 900, which outputs a stepped (simulated) sine wave. When AC power is lost, the machine loses power immediately, even though the UPS battery is fine. It was suggested that I need a pure sine wave output.

See my thread: http://en.community.dell.com/forums/t/19271845.aspx

Michael

Thanks for the response Michael. I read your other thread. So far this seems to be an unresolved issue. Checking the APC website, I find that the Smart UPS series is not a true sinewave either, or at least not all of them. For example, here's one of the lesser expensive models which states that it produces a "stepped approximation to a sinewave."

http://www.apc.com/resource/include/techspec_index.cfm?base_sku=SC1500

Since I'm actually more interested in the voltage regulation ability of the UPS, as opposed to its ability to run the system for longer periods of AC power loss, I'm not wanting to put more than about $200 or so into a unit. If it gives me enough time during a power failure to safely save and shut things down, that's all that's really important to me.

I have to wonder if the 435T truly doesn't like these pseudo sinewaves, or if the problem is something else related to particular models of UPSs, and that there are assumptions being made regarding the sinewaves. I've been reading all the reviews on Newegg and Amazon, and lots of people are using both APC and CyberPower UPSs on their computer systems, apparently quite successfully. An interesting spec would be to know how long of an AC power dropout it takes before the system loses everything and shuts down. This, of course, would be measured in milliseconds and would be dependent on the instantaneous load and the size of filter capacitor in the power supply. If the UPS didn't make the switchover fast enough, it might explain the problem. I suspect that in the interest of saving money, Dell may have underdesigned the power supply. Some older PS designs might hold up a few milliseconds longer in a power outage, providing just enough time for the UPS to take over. Just thinking out loud.

This PC sold with two power supplies -

N248K Power Supply, 360 Watt, Power Factor Correcting, Foxconn
N250K Power Supply, 360 Watt, Non Power Factor Correcting, Foxconn

It would be interesting to know which one you have installed.

Actually it was sold with a 475 watt supply. There are no numbers similar to those you gave above, but here's what is on the only label on the supply:

CN-OF21J-73245
91L-264-A00
DP/N F217J

There's a possibility that I might have mistaken zeros for "O"s, or vice versa in the above. The print on the label was extremely small.

Dave

Actually it was sold with a 475 watt supply. There are no numbers similar to those you gave above, but here's what is on the only label on the supply: CN-OF21J-73245 91L-264-A00 DP/N F217J There's a possibility that I might have mistaken zeros for "O"s, or vice versa in the above. The print on the label was extremely small. Dave

I also have the 435T with the 475w PSU. My computer lost power last night for the third time in the week I've owned it. The UPS software (PowerChute) reports that the battery is in good condition. I verified that everything is plugged into the correct outlets. So I'm suspicious of the interplay between PSU and UPS. Of course, the only way to be sure is to buy a pure sine UPS and try it out, which given three power-downs in a week is something I'm pretty close to doing, unless Dell is able to tell me that the PSU is indeed incompatible with simulated-sine wave UPSes.

Michael

Dell Part number F217J and Flextronics part number VP-09500073-000

Product Safety, EMC and Environmental Datasheets

If you come across a true sinewave UPS with voltage regulation for a reasonable amount of money, please post a note back here Michael. It would be greatly appreciated.

My bad, was looking at the MT. The T only had the one 475w Power Factor Correcting power supply.