The food in the microwave is not heating up I have tested the fuse (F8AH250V) and found that it has blown. Is it safe to replace this fuse (F8AH250V) on my microwave.

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https://www.ifixit.com/Answers/View/285420/Daewoo+microwave+shines+but+does+not+heat

Time for a new microwave.

If there is spark please do not switch on unless you have confirmed the fault. It is possible that the Magnetron is leaking and sparking to the ground. As you have mentioned it was stored, it is quite possible that insect can get into the oven and create soft spots. When you switch on these will create a short and make the voltage jump and in the long run damage the magnetron.
So Remove cover after disconnecting , check for dirt/moisture in the cabin, if so wipe clean and dry, check the magnetron and area clean and use an jet air to clean off.
Now switch the microwave power on and use a cup of water to test.
If you notice any sparks shut off as the magnetron or the main HT capacitor can be faulty. Replace with same type. If not check the waveguides within the cabin for food particles that can burn and spark, check for rust that can corrode and spark when the ceramic paint has worn out.
If there is heating without any issues, you can use the microwave safely

Click on replacing waveguides: http://www.espares.co.uk/advice/microwave/a/5/1146/how-to-replace-a-microwave-guide-cover.html

9 times out of ten it is the magnatron that has gone bad, that is the device that creates the microwaves for heating the food. Check inside the cabinet for fuses and if none found or blown then it is the magnatron. These are available widespread but most cost about as much as a new oven, so do a google search on your make and model of microwave and search for a magnatron for that unit. This will bring up parts suppliers and their prices and you can decide if it is worth fixing or replacing

Does not heat food means a problem on magnetron tube and fuse blown in high voltage area. Have it replaced and it will heat again.
I hope I answer your problem.

Took microwave out, opened back, 15amp fuse blown. Replaced all ok.

you can use any 8 amp fuse of that caliber even a bit larger if you had to.
Phil

it is obvious that nthe microwave side of the unit is not working.
microwaaves have a terrible habit of blowing fuses for the most stupid reasons. No not the fuse in the plug but the ones the manufacturer hides inside the case, you will have to look hard. if one is blown replace it with a direct replacement. and do not test the machine with the cover removed

open the casing and replace the blown fuse.there are several so check them all. probably why the machine was in the auction

I'm assuming that it doesn't microwave either. If it does...then the heater is bad. Sears parts sells them. Second guess is a blown fuse or thermosensor. Inside the pad housing, locate the internal fuse and replace it if blown. The thermosensor is a black plastic bit about the diameter of a dime and 3/8 inch thick and clamped to the side of the unit inside the control area. Test it for continuity and replace if open. If not either of these, then you have power supply issues or control panel problems. My bet: the heater blew out. Often, this is caused when you heat greasy foods.

sam..vane...two different problems.

Sam...find out if you've got power in the outlet you're using. If not, you've got to check to see if you've got a blown fuse in the unit. Also ...see below.

vane...chances are you have a power issue or the thermosensor which is used for a safety has blown. It is the size of a dime and 3/8 inch thick...black...two wires. You'll probably find it has opened. Found attached inside the control area to the side of the microwave heating area.