The owner's manual is designed to help you operate the unit safely, but of course the silly manufacturer does not want to expose himself to any legal liability by trying to help you troubleshoot and repair such a lethal product in case you are not technically trained and experienced.
That said, here is some helpful info:
A microwave can be dead for many reasons.
If it goes dead for a while during or after cooking then comes back on, the magnetron is probably overheating and causing the magnetron thermostat to open. Then when it cools, it closes the circuit and allows power through again.
If it's intermittent or random, it may be a bad connection, usually on the control board or fuse holder.
If it went dead almost immediately after pressing the Start pad, that's usually a shorted high-voltage capacitor.
If it went dead a few seconds after pressing the Start pad, that's usually a failing high-voltage transformer.
If the fuse is good, it may be an open thermostat or thermal cutout on or near the magnetron or on top of the cavity / body of the oven.
If you or a friend decide to look into it, we have critical safety information and disassembly information at our site, linked here on Fixya:
http://tinyurl.com/yzjozk
Please write back with more details if you need further help.
We're happy to help and we appreciate your thoughtful rating of our answer.