Well, well. I had excatly same component broken. It is Schotky rectifier diode with common cathode in TO-220 can. Its electrical specs are 2x5A, 100V reverse voltage. My replacement part is specified as 2x10A, 150V reverse voltage (Vishay VS-20CTQ150-M3). I also added small heatsink, because the diode is either overheated or there is present destructive voltage spikes from switching regulator and transformer. Two similar breakdowns in one internet page are not coincidence. This is definetly first thing to check, when system does not lit-up at all. The problem is easily detectable from DC output connector even without power by using diode measurement option. The heart of the PSU is already obsolete FSGM300N SMPS converter circuit. The desig resembles very closely application circuit presented in its datasheet and is helpfull when one debugs the system. The diode mentioned above is D201 in schematics. In power supply there is only one output voltage so you may omit 5V output from the schematic. As a...