VERY SERIOUS WARNINGS:
1. Not only is this a mains-powered device, it can contain extremely dangerous high voltages. The capacitor that drives the magnetron has a built-in bleeder resistor for safety but do not rely on it!
2. As the first stages of this growing i'ble involves disassembling the magnetron, you must also be careful that you are not exposed to a toxic chemical----beryllium oxide which, if inhaled, can cause incurable damage to the lungs
3. Because these cheap "consumer" devices are assembled with self-tapping screws, also be aware of getting metal splinters in your fingers.
The appropriate steps will be highlighted as they are encountered.
The magnetron had failed in this unit, otherwise everything else was working. This is characterized by the gradual decay in efficiency (e.g., ever longer cooking times) over a period of time. Having the magnetron properly replaced usually costs more than purchasing a replacement oven. So this is the first item to be removed.
Step 1: Open the Case
As this is a reasonably nice stainless steel case that is destined to replace my very under-sized mail box, I have been careful in handling it to reduce scratching.
Note that most of the case screws are at the back, but sometimes they can be on the side, and even underneath. See the red circles. As this case is to be re-used, keep these screws. The extra holes in the side toward the front of the case are for a wall-mount bracket and, for now, can be ignored.
Step 2: Discharge the Capacitor!
Although it was known that the magnetron was dead, this unit had still been recently powered to check that the high voltage circuits were working for a further project -- an ozone filter, which will come later. Therefore, it was definitely in my own interests to make sure that capacitor was really discharged!
You can see a sturdy pair of pliers used to short-circuit the capacitor. You'll also observe the appropriate warning on the step-up transformer.
Step 3: Fairly Routine Disassembly From Here
The red circles indicate: two safety thermostats, the interior light and a grill element. These were all unscrewed, but left connected, except for the grill--those wires were removed all the way back to the control board.
There are two crimp connectors leading into the bottom of the magnetron. Simply disconnect these. The magnetron can be removed by removing four or five screws. As this is a wasted magnetron, these screws can be discarded.
Treat the magnetron as a very fragile device!
If it requires any force to dislodge it, look for another screw.
Step 4: Tackling the Magnetron
WARNING! That pink bit which looks like a form of ceramic is highly toxic. This is the beryllium oxide that I mentioned in the Introduction. Avoid scraping or breaking it at all costs as, like asbestos, anyinhalation is too much. It is not always pink. I have seen it in black or white as well. As long as it remains undamaged you are quite safe.
The easiest magnet to recover is the "inside" one. Simply pull the heatsink cage forward, which reveals more toxic pink. If you pull far enough, you are unravelling some coils of copper from inside the rear chamber. Once they are long enough cut them with pliers and separate the two parts. This magnet will then just lift out without any difficulty.
Step 5: Using Extra Caution to Get at the Second Magnet
Now the second magnet will just lift out.
If you are a responsible i'bler, you have a toxic waste collection bin, don't you? Dispose of the center heatsink section as toxic waste. Don't even touch the pink bits!
Step 6: What Has Been Achieved So Far
These may not be the strongest magnets in the world but they can pinch your fingers! As I accumulate them for myself, they have turned my fridge door into a filing cabinet.
Note that the magnets from any one Microwave are rarely the same thickness. This is the first "pair" that I have encountered which has different diameters as well.
Treat your magnets with care. Slamming them together can shatter them.
If your original Oven was in the same condition as the one I used, you still have other useful stuff that will be addressed in future instructables, which will refer back to this one.