I have never sorked on a Lisa (if someone wants to donate one....), but I would start out by regardign them as normal SMPSUs and faultfinding accordingly. Check the internal fuse. If blown, look for shorts in the rectifier diodes or chopper. Check low value resistors in this area too, which may well act as fuses!. See if you can find a startup resistor (a few hundred k from the +ve end of the mains smoothing cap to some point in the chopper circuit). It may well be open. Something before the power control 'switch' (is this a relay or a triac, or something?). Maybe a leaking capacitor in the mains filter circuit or something like that? A short circuit on the output side? Maybe a shorted rectifier or a leaking output-side capacitor. Or maybe the current sense circuit is malfuncitoning and detecting an overload when there isn't one. But don't be tempted to disable it!. Or maybe the crowbar is trippinf and shutting the supply down due to a problem in the voltage regulation loop. -tony