My microwave Dacor DMW2420S is making a loud noise and lights flashing. It started after using 50% level for melting butter. Any suggestions?

SOURCE: Microwave makes a loud noise while using.

After you turn it on, it's a loud noise like it's coming from the fan, but other then that it works wonderfully.

SOURCE: Microwave won't heat/Makes buzzing noise.

The symptoms you are describing are typical of a magnetron that has gone bad. Continuing to attempt to use the oven in its current condition can cause further damage. So, I would recommend not using it. Microwave ovens are considered dangerous and repairs should not be attempted by anyone that is not electronic saavy. The High Voltage Network inside the oven has voltage potentials of 14,000 volts and higher. If you feel this is something you wish to attempt, the Magnetron part number is 1156751 and costs approx. $158. Keep in mind, if the magnetron has been arcing and making a burning smell you may have burned the protective coating that lines the walls of the waveguide. If the waveguide is damaged it is not repairable. I do not know if this is a replaceable item on your model microwave. Double check your warranty information and/or owner's manual. In many cases the magnetron is warranted for several years beyond the limited warranty that comes with most appliances. Post back with comments and let me know if you want me to assist you further. In addition, if you provide me with your EXACT model number (located along the door opening) I can narrow down parts a little better. I know this all sounds discouraging, but I do hope I have been able to help you.

SOURCE: Kitchenaid builtin microwave buzzing

I would recommend changing the diodes as well. This will usually take care of the problem.

SOURCE: loud humming noise

If all of your door switches check out, replace the magnatron, capacitor, and diodes.

SOURCE: Microwave not heating food and is making loud noise.

You have burned out the magnatron (heating element) which is common on GE microwaves. most service companies will charge about 200-250 to replace it