Thanks for a reply .
Yes the magnetron goes within seconds. It has a louder than normal hum and you can just tell something is getting Fried . I can't see in the wave guide . My thought also was that its getting way too much power. Don't know where to start though . Can't find any service info, schematic, nothing. I'm new to microwave repair, but with a little info on what I'm looking at, I can usually figure things out. I'll guess the 'inverter board' is what the transformer is sitting on. It's a 4"x4" circuit board and the red wires going to the magnetron come off the edge of it . It has a lot of other 'parts' on it too. One other thing, I noticed a nick in the paint inside the microwave on the bottom . There is a minor bit of exposed metal . Never saw any arcing though so for WIW. ?
Thanks for your help.