I have a 721.63263300 counter top SS unit

What kind of microwave oven is this? A counter-top model or an over-the-range microwave? Do you have a brand and model number? And which light bulb do you want to replace - the cavity light bulb, or the bottom light(s) of an OTR microwave?

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It is quite possible the magnetron has burned out, when it arcs it puts a tremendous strain and causes it to overheat very quickly. On top of that you found a burned mark behind the pad which is not good, so there are least two problems that must be addressed perhaps more. In any case it may be cheaper to replace the microwave oven at this point.

Issue with your Main Panel Power Fail to innitiate ..Du to Component mal-functioning inside the unit ...Possibility Magnetron defect, Or main Transformer Over heat, Also check for safety swich on the door for bad connection...

if there are not light there are usually two fuses in the unit one where the power cord comes into the unit and one that goes when the unit gets to hot. if the unit if a counter top unit you will need to go buy some safety star bits for the hardware store to get the cabinet off. just check the fuses with a ohm meter.

We have a similar problem! It sounds like a problem with the microswitch inside the unit that the door is suppose to engage when closed. If not engaged properly, it will not cook. We had the switch replaced last March but it has started acting up again. We can press in on the door and/or lift it slightly and it will cook. Try putting time on the counter and hit start. It the word "cook" appears then try moving the door slightly and see if the turntable starts turning. If not, then you may have a more serious problem. Good luck!

Probably a fuse inside the unit. Can be caused by overheating or by door switches not working properly.

You'll have to try to adjust the switches. Kind of hit and miss thing. You can usually get at them from taking the grill off the top then take the one screw out of the control panel on top. The you can see the switches where your door hooks go into. Try moving them around a bit. That's about all you can do. They really don't have a lot of adjustment. Hope that helps.

HI, when the Magnetron becomes unstable, the microwave will not heat anything. simply replace the Magnetron. This device creates the heating action and it is damaged and not functional at this time.

Hi firstly to see if it is producing energy, buy some 5mm light emitting diodes from an electronics store. cut off the leads close to the plastic body.
place in microwave and put on cook for max 10 secs, if the led's light up you have microwave energy, shut off the oven as soon as they glow otherwise you end up with a mess.
If you have energy then your problem is most probably the door interlock micro switches which after time do not operate properly. let me know the results and we can go further.

We see this a lot. The problem is on the control panel, which we regularly repair nationwide for $39.95 postpaid.

This light failure often occurs when a bulb goes out and the filament shorts, or when the bulbs are removed or installed without first unplugging the oven from the power line. Either can cause such a failure on the controller.

Details of our service and critical safety information and disassembly information is at our site, and our link is at our listing here on FixYa: http://tinyurl.com/yzjozk

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