[Lenwood1]

Since the Timer, Clock and all Interior lights work; The Heating is all that's missing. Please tell me Where and How to Replace the Tube...Thanking you

[PS Volunteer - Appguy]

Sort of rare these go unless it started to arc and smoke!! Most probable failures are high voltage diodes, control electronics.
If you are sure that is your problem then
Remove outer panel and short high voltage capacitor with a jumper wire, then disconnect all wires to magnetron and unscrew the nuts from it and pull out. Check the condition of the rf seal at base of magnetron and inspect waveguide to verify no burn marks.
Also sometimes a mica diffuser will smoke and burn right at the waveguide entrance to the oven cavity. Make sure to note where wires go where. If you put the wires in the wrong places you will get a blown fuze or a nice light show!!

[Lenwood1]

I appreciate your information. I was told, it's most likely the Magnetron. There was never any smoke or indication of anything being burnt-out. I set the convection as usual and it never started. There is a cilck/thump sound shortly after the start button is pressed. A subtle click after the start button in pressed in microwave mode. The timer works just fine. When door button is pressed the timer stops counting down and after door is closed and start button is pressed; timer starts from point it stopped. I custom build computers and have worked on TVs; yet am unfamiliar with Microwave Convection Ovens. I need as much help as I can get.....