Here's a cheap ATX supply schematic: http://www.pavouk.comp.cz/hw/en_atxps.html It's 200W ATX, but the 300 and 400 watt supplies are very similar. The 120VAC is doubled (or the 220/240 is left alone) and then rectified to about 300VDC. The switcher then takes that and converts it and isolates it for the lower voltage needs. It used to be that the 12V line was regulated, and the others simply depended on the transformer windings, but newer supplies may regulate a different voltage. -Adam On 11/1/06, Alan B. Pearce wrote: > >I have a few new ATX power supplies that have a real PFC input stage and > >really are universal input. > > I would be very surprised if they were done any other way, with modern > switch mode chips available. > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > -- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Moving in southeast Michigan? Buy my house: http://ubasics.com/house/ Interested in electronics? Check out the projects at http://ubasics.com Building your own house? Check out http://ubasics.com/home/ -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist