DECserver 200MC circuit diagram

Assuming this is a switch-mode unit, have you checked the obvious suspects? Start by looking at the fuse. If it's blown 'softly' replace it and try again. If it's shattereed or blackened, then suspect a shorted semiconductor device on the mains side of the PSU. Either the rectifier diodes or a chopper transistor. If the latter, then it's possible some other component (snubber capacitor, chopper trnasformer) has failed and taken the transistor with it. If the fuse is good, then it's possible (probable?) that the startup resistor is open. Look for a high-value resistor (hundreds of k) -- maybe 2 resistors in series -- from the +ve side of the cmains smoothing capacitors to a point in the chopper driver circuit. If you find such a resistor, test it. -tony