Sharp KB-5121K won't heat -- everything else works.

You should check for 3 volts on sec coil supply for magnetron but do this check with the hv capacitor and hvr disconnected if 3volts is present , most probably your magnetron is deffective, replace it with the same type

I typically find it is not door hinge issues but door switch issues, especially with sharp. You may heve a little movenent in the door hinge and that is allowing the door hook to move up and down on the plunger for a door switch that is probably a bit melted due to bad connections. If you check the door switches and look for any browning around the terminals where the wires push onto the switch you will probably find an overheated connectoion. Replace the bad switch and run better wires and better termninals to the new switch and it will probably be fine.

The problem is in the magnetron, "heart of the microwave oven" or the inverter board if the system is less than 7 years old.

This a common problem, the likely cause is a bad magnetron "heats food" and is the heart of the microwave oven, if the item is five years or more, cheaper to replace.

This indicates three parts that can be the culprit, the magnetron "common problem" or the high voltage capacitor or diode, all three work together to heat food. Depending on the nature of the repair will determine the price for parts and labor and may approach the cost of a new one.

Sounds like the magnetron died
$101.99 from Sears Item # 1-11 on this diagram

http://www.searspartsdirect.com/partsdirect/part-model/Sharp-Parts/Microwave-Parts/Model-R320HW/0958/0123245/P0405112/00002?blt=06&prst=&shdMod=

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Here is a tip that will help you to figure out what is wrong with your Microwave Oven....

Microwave Oven Basic Troubleshooting Tips

heatman101

If it runs and makes normal noise but just no heat, issues is either a loose connector to magnetron or at diode to capacitor. Be careful with capacitor because it stores thousands of volts.

The fact that the microwave and convection both do not heat indicated that the oven is in demo mode, check the user manual, otherwise it will possibly be a relay not triggering, may need a pcb replacement, check Demo mode 1st....Phil

Hi,
Here is a tip that will help you to figure out what is wrong with yourMicrowave Oven....

Microwave Oven Basic Troubleshooting Tips

heatman101

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