I had a 270 that went bad last week with this issue. Once I found out about the capacitor issue, I found another 280 that died a few months ago (one day after the 3 year warranty expired), they both have replacement motherboards in them now.

Unfortunately Dell isn't replacing power supplies that are damaged due to the motherboard. My 270 also ruined the power supply. I ordered a replacement (about $40 with shipping), but it might not ship for another week. 

Does anyone have a spare Optiplex 270 power supply?    (the one from the 280 doesn't work in a 270)

thanks

-John