Sharp Microwave Not Heating

[TechnicianBrian]

Model #R-520LW-T, this unit stopped heating and another technician diagnosed the problem as a bad magnetron tube. After replacing the mag the unit still didn't heat and the tech wasn't sure what to do next so I got involved. When looking over the unit I verified 118vac was going to the high voltage section so I knew all the components up to that point must be functioning properly. I then began to check the HV components and came across a wiring problem where the two leads to the magnetron were reversed. It looks like the other tech correctly diagnosed the failed magnetron, but by mixing up the two wires caused a failure himself. I returned the wires to their correct position and the unit now heats fine. Just a quick note: if you remove wires, make sure you know where they belong when reinstalling as it is not always obvious. Also, ensure the HV capacitor is discharged before touching anything in this section. Better safe then sorry.

R-520LW-T

[JWWebster]

Brian how do you know which is which when hooking up the mag?

[TechnicianBrian]

I am glad you asked JW.  If the magnetron has a connector with a single wire and a double wire, the single wire connects to the terminal labled 'F' while the double wire connects to the terminal labled 'FA'.  If there are only single wires, the one coming directly from the HV transformer connects to terminal 'F' while the one that comes from the capacitor will go to 'FA'.  Easy as pie.