Microwave blowing fuses when setting programme

Based on you information, if you disconnected magnatron and unit ran with no fuse problem, I would suspect magnatron. You should consider the age of unit it, may be be a better alternative to replace it.

If it keeps blowing a fuse then there is something that is causing the current spike blowing the fuse. I would run a full diagnostic or ask a qualified electrician. Something else is most likely blown and replacing a fuse would probably just feed the problem.

you can use a 250vac 20 A ceramic fuse but the right size is engraved in one end of the fuse any radio shack or electronic store will have it make sure it is disconnected.

Normally, if it was running and the fuse blows, it is then an electrical/electronic fault. If you simply woke up to the fuse being blown, then very possible it is only the fuse from a cocoaroach or the like.having gone onto a live part of the circuit. Pull the plug out and remove outer cover. Locate the fuse on the board where the power wire comes in and replace for the same value (normally 12 amps).Switch on and try with water in the microwave. Please stand clear when testing as the power is huge in the system. If it blows again, really, get a technician that knows what to look for when trouble shooting. 50% of the time it is the capacitor and HVdiode. Other 50%of the time it is the magnatron. Careful testing can ensure the right part first time. Microwave is one of the most dangerous appliances next to a tv set that i have found.

The fuse is located inside the microwave. You will need to remove the front panel to get to it. It will be located on the black power wire inside the microwave and installed inline. Make sure that the microwwave is unplugged before removing the front panel. Once you locate the fuse inside you will need to remove it and test it with a continuity tester to see if it is blown. If it is make sure you replace the fuse with the same amp rating you found. If the new fuse blows again then there is an electrical short somewhere inside the microwave.

replace the fuse see if it blows again you can get those at radio shack 250 volt either 15 or 20 amp get 3 or 4 of em

e 10 is the internal safety fuse has blown this often happens if door is altered for any reason moving the door can effect the setting of the monitor switches these are set to a high tolerance to avoid operation of microwave with door open changing the door has shifted these settings and blown the fuse, replacing the fuse may be enough to get it going but it should be checked for leakage.

Q - The microwave makes a loud "hum or buzz" noise but will not heat up the food?
A - 9 times out of 10 this is usually this is a bad magnetron, the other time is sometimes a bad high voltage diode. See components section.
 
 
Q - My microwave is running and sounds like it is working but will not heat up anything.
A - Many thing can do this but, common things are....loose high voltage wire.....poor solder joint on board.....magnetron.....power relay.....
 
Q - The microwave display counts down and the inside light is on,  but nothing is heating and the fan is not running.
A - This most commonly is a bad door switch, other possible problems are a faulty relay or solder joint on the power module, but a bad door switch is most common.
 Q - My microwave went dead when I opened the door ( same problem as closed the door ).
A - This often is a stuck or faulty door switch and it has blown the interior microwave fuse.
 
 
Q - My microwave is completely dead.
A - House fuse has blown or interior fuse inside the microwave has blown ( usually a part inside the microwave makes this fuse blow ) Sometimes a bad fuse holder inside the microwave cannot hold the fuse tight enough and the fuse will blow as well. 
 
 
Q - The fan in my microwave oven is not running will this hurt my microwave?
A - YES, the fan cools the magnetron and electronics, take the microwave in for service, most fans are not too expensive to replace.
 
 
Q - My microwave blows the fuse inside itself as soon as I push the start button.
A - Usually a shorted high voltage capacitor...see components section.

the panel display is fried. you'll need to remove and replace it...this the sort of thing you enjoy doing?

You say when you "power on" the fuse blows? If that means when you hit the START button to cook, then you probably have a shorted high-voltage capacitor. If you mean it blows when you plug it in, you probably have a shorted door switch. Your microwave may also have a wiring diagram pasted on the inside of the outer wrapper or in an envelope. That will help in your tests.