On Wed, 6 Aug 2008 19:13:07 -0700 "Tobias Gogolin" wrote: > Or can anybody think of some tricks that may be applicable to make any > old PS work on 120V DC? There is some variation in PS philosophies... Switchable 120/230 supplies (older ones) normally change the configuration of the input rectifier to multiply the input voltage on 120V, and just rectify on 230V. Those will be near impossible to adapt. Then there are 'full range' or 'universal' ones, that are designed to cover the entire range from 120 to 230, without any switching (and normally don't multiply). If they're specified as 90-240V they just might work on 120VDC, except for the overheating problem (see below). But even single voltage 120 V AC supplies, when rectifying actually generate some 160 V DC. If you connect just 120V, it may not be enough to drive the PC. And, by connecting DC, you only use have of the bridge rectifier which might overheat two of the diodes. You might try to open an old 120V only PS, and see if you can detect the number of primary windings on the ferrite transformer, and remove a few (say, about 20-30%). It won't be easy, as the primary is frequently below the others. If I were you, I'd also connect the DC directly, without the rectifier. Maybe a small resistor wouldn't hurt to protect the input capacitors from too high currents. John -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist