KitchenYou will see this often
Microwave oven
Also called microwave.
Two different machines in one cabinet: a useful slow motor and some heavy door switches, and a high-voltage section that kills people. Take the motor and the switches. Leave the transformer, the capacitor, and the magnetron alone unless this is already your trade.
A donor is the dead machine. The parts below are what is still worth removing from it. “Leave it” is a part that is physically in there and should stay in there: too dangerous, too worn, or only useful as part of a repair you are not doing.
The turntable motor under the floor and the door switches in the latch are ordinary, useful parts. The side cage holds a high-voltage transformer, a capacitor that stays charged, and the magnetron. Leave that cage alone unless this is already your trade.
Why it is in the trash while the parts are not
A dead keypad, a blown fuse, or a turntable that stopped. The high-voltage section may still be live-capable. A blown fuse often means the monitor interlock was abused.
Before you open it
Do this while it is still unplugged, cool, and not leaking. Unplug. The high-voltage capacitor can remain charged. If you cannot identify that capacitor and discharge it through a resistor, do not go past the turntable motor and the control panel.
Where the dead machine usually is
- Kitchen — In the house
- Bulk trash day — Curb
- Move-out week — Curb
On the curb constantly. Do not open one in a living room.
How it comes apart
The turntable motor is under the floor, reached from the bottom or by lifting the floor panel, and it is not in the high-voltage cage. Door switches are in the latch. The cage at the side is the part you are declining.
Tools: Phillips, Nut driver, Meter, Discharge resistor if you are qualified.
Words on this page
- interlock
- A switch whose job is to stop a machine when a door or cover is open. Take it for a new project. Do not bypass the one still fitted to a machine you will use.
- capacitor
- A part that stores a small amount of electrical energy. Large ones in power supplies can stay charged after you unplug. Discharge them before you touch the leads.
- transformer
- Two coils on an iron core. It changes voltage and, in a proper one, isolates the output from the wall. Heavy old adapters are this. Microwave oven transformers are a different, dangerous kind.
What to take
The table is the short version. The notes under it describe that part inside this machine, not only the general description.
| Part | Call | How many | How often | Where to look |
|---|---|---|---|---|
| AC synchronous gearmotor | Prize | 1 | always | Under the turntable. |
| Microswitch | Prize | 3 | always | Door latch. |
| Fuse | Worth pulling | 1–2 | usually | On the line input. |
| Thermal fuse | Worth pulling | 1 | usually | On the magnetron housing or the cavity. |
| Shaded-pole motor | Worth pulling | 1 | usually | Cooling the magnetron. |
| Mains cord | Worth pulling | 1 | always | Rear. |
| Tactile switch | Bonus | a pad | usually | Keypad. |
| Iron transformer | Leave it | 1 | always | High-voltage cage. |
| Electrolytic capacitor | Leave it | 1 | always | Beside the transformer. It is not electrolytic; it is a high-voltage film capacitor around 1 µF at over 2 kV. |
| Neodymium magnet | Leave it | 2 | always | On the magnetron. |
Prize
Mains synchronous gearmotor, a few RPM, marked 120 or 230 V.
Under the turntable.
Two screws, a connector. This is the one to take.
Usually perfect.
Mains-rated interlocks. One is a monitor switch arranged to blow the fuse if the door switches are defeated.
Door latch.
Label each wire before you disconnect. Do not reinstall the oven without them.
Good.
Worth pulling
Ceramic mains fuse. Replacing it without finding the fault is how the new one opens.
On the line input.
Read the rating.
Often open, which means it already did its job.
One-shot, temperature stamped.
On the magnetron housing or the cavity.
It is a protection part, not a thing to bypass.
Open means the oven overheated.
A small mains fan.
Cooling the magnetron.
Take it with the blade.
Good if it spins freely.
A proper appliance cord.
Rear.
Inspect the grommet.
Good if not cracked.
Bonus
Membrane. Usually the part that failed.
Keypad.
Not a prize.
Worn.
Leave it
The MOT is a ~2 kV transformer. It is not the doorbell transformer and it is not a bench supply. Unloaded, it saturates and the current is lethal.
High-voltage cage.
Leave it in the cage.
Dangerous.
It holds a charge. The bleeder may be open.
Beside the transformer. It is not electrolytic; it is a high-voltage film capacitor around 1 µF at over 2 kV.
Do not take it home 'in case'.
Charged.
Strong ring magnets. The ceramic in the tube can be beryllium oxide.
On the magnetron.
Do not machine the tube. Prefer hard-drive magnets, which are a better shape and not attached to BeO.
Magnets are fine; the tube is not your project.