You don't give us much to go on :-) What are they doing? In general you'll either get mo outputs at all, or a supply that's tripping. It will 'tweet' about once a second. If you get that, connect a voltermeter (or better a 'scope) to each output in turn and see if one of them is not coming up at all (if so, then suspect shorted secondary-side components on that output). If it's totally dead, look at the mains fuse. If it's shattered/blackened, you have a major short on the primary side. Check the rectifier diodes and chopper transistor, etc. If it's gently blown, replace it and try again. If it's OK and the supply seems dead, suspect a startup failure. Often there's a high-value resistor from the +ve side of the mains smoothing capacitor to some point in the control circuit to get it going. That resistor (may be 2 in series) often fails open-circuit. And don't overlook the obvious. I've just spend some considerable time debugging a very complex HP SMPSU (on 6 PCBs, with 5 chopper transistors, etc -- the supply in a 7245A printer/plotter), only to find the fault was that an intneral cable wasn't plugged in properly. -tony