Usually the magnetron goes bad first & causes the inverter board to fail. 99% of the time on these when there is any no-heat issue or f-7 code I replace the magnetron AND the inverter board. You probably have a bad magnetron which is causing higher than normal current draw through the inverter board. Usually this damages the inverter board. Like I said, replace them both.
well if you had read the post i made fully you can see i am not getting the F7 code, i only got that when running the test and the code was part of the test. (its because of the added resistance of the DMM measuring current to the mag from the invertor board.) i got the code as expected but the current values were all wrong.
but i do have an update! the oven is not repairable. i replaced both invertor and mag hoewever had i looked in the waveguide behind the cover sooner i found that one of the Rectifiers (small chunk of metal suspended from the top of wave guide) was melted and looks to have been arching against the top of the cabinet (wave guide)
unfortunatly i had to pay a technician to come out to diagnose the problem even though i already knew what was wrong in order for whirlpool to agree the oven was not repairable.
so basically i had to pay a tech to come out and stand there to look important and after i explained what i had done, he agreed it was not repairable.
whirlpool has agreed to replace the oven at a pro rated cost to me of 350 bucks.
appliance parts pros has received the parts i did not use and i am waiting for them my refund of the mag and invertor board.
they tell me they will take the parts back and no restocking fee. just refund my money which i think is pretty cool.
in the mean time whirlpool had me sign a form that dispose of the oven but before i did that i took the magnatron, the invertor board, relay board and all the sensors as well as the interlock switches for the door out of the unit just in case i have another problem in the future with the new oven.
i plan to get the extended warranty this time so if i have another failure they can pay for the service calls and parts or a new oven at no charge to me.
of course with the warranty i know it will now never go bad again.