U most
definitely have a failure of the
magnetron, i have no idea what this
diode fix is, so suspect it is an urban legend, read many such things on
fixya, in any event it is an expensive part so
here is how you test the magnatron:
Testing a megnetron:
NOTE: Before you test this component, make sure your microwave is unplugged, and that you have
discharged the capacitor.
There are two tests to conduct in order to determine whether or not a magnetron has become defective. If you receive results other than what are detailed below, you will have to replace your microwave's magnetron. Each test is described for you here:
TEST 1: Locate your magnetron and label each of the wires attached to it so that you know which wires are to be replaced where. Set your ohmmeter to the lowest resistance scale. Take a resistance measurement between each of the magnetron's terminals by touching each probe to one terminal each. Reverse the probes and take a second resistance measurement. Each measurement should read less than one ohm.
TEST 2: Set your ohmmeter to its highest resistance scale. Touch one of the meter's probes to a magnetron terminal. Touch the other probe to the metal magnetron housing. Take special caution to not touch the two probes together. This could result in an inaccurate reading. This test should produce a reading of infinity - indicating an open circuit.
If the magnetron is defective here is the way to replace it, the oven must be removed from any built in enclosure.
As far as replacment goes have a certified and experienced appliance repair technician examine and replace your magnetron. This task is much too dangerous for the average layman to perform on his own.