microwave dead, after cooking vegetables in water?

My oven was completely dead, no digital display etc, i replaced the 8Amp fuse on the circuit board sitting above the cooling fan, the interior light came on and so did the digital display, I set up the hours & minutes and after putting some food inside and selecting the cooking time, i pushed the starter button, the oven came on as normal but went dead 2 seconds later, can you please advice where I should check for faults?,I am a retired electronic and technical engineer, but I cannot get an exploded view diagram to troubleshoot the prob.