MODELNUMBER R 930AK THISMICROWAVE BLOW A FUSE WHEN YOU HIT THE START BUTTON WHAT COULD BE THE PROBLEM

high voltage is blow due to over heatered..replace high high voltage fuse..

The magnetron has a short, or the inverter board, "if 7 years old or less"

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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you might need to replace the door switch

For that problem I would check the sensors. If the sensorblock is faulty, it will think it is hot when cold etc.
Hope this helps.

We have the service manual for this model and have uploaded it for you here.

You can order parts for this brand from Encompass here or you can call them toll-free at 866-779-5835.

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The magnetron (the part that heats the food) is probably done, they tend to go out if the fuse didn't blow and it usually isn't worth fixing as the cost of the magnetron is almost what it would cost to buy a new microwave.
Sorry for the bad news.
Benjamin

Is it totally dead? No display? Or just does not cook? If it made an unusual noise before it 'died' something probably shorted out.... You need an ohm meter to troubleshoot. If the fuse is open, switches and HV circuit need to be checked before replacing fuse. Sometimes on the convection Microwaves (not just Sharp) the fuse will 'rust' and open rather than blow. Or the fuse holder can over heat and fail.

You need to open the oven (unplugged) by removing the screws along the case. Inside, there is a 20 amp fast blow fuse that you can get at Radio Shack. It looks cylindrical and white. I would test that first. However, replacing the fuse may work, but then, other components may have shorted inside causing the fuse to blow. Try the fuse replacement/test it first. Good luck

If it blows the fuse as soon as you hit the START button, it's almost certainly a shorted high-voltage capacitor.

If it blows a few seconds after you hit the START button, it's probably the high-voltage transformer. You'll possibly also smell a faint electrical burning smell from the rear vent after you shut if off.

If it blows the fuse as soon as it's plugged in, you probably have a shorted door switch, a shorted varistor, or an internally exposed wire shorting to the chassis, etc.