Here are the internals of a cheap Microwave/Convection Oven combo. Electronics bay is pretty much the same as a standard microwave, with the magnetron, transformer & diode/capacitor voltage doubler, with the addition of an extra fan & a pair of nichrome elements to provide the convection oven function.
Convection Fan
Convection blower which keeps the cooking vapours & smoke away from the elements, & circulates the hot air around the cooking chamber. This is a 12v DC centrifugal type blower.
Convection Element
The elements are inside this steel shield, air duct extends from the centre.
Thermal Cutouts
This oven has a pair of thermal switches on the magnetron.
Capacitor & Diode
The usual capacitor/diode voltage doubler in the magnetron power supply. The transformer is visible to the left.
Controller
Electronic controller PCB. This has a pair of relays that switch the elements & the magnetron transformer.
Here is a cheap no frills microwave oven, which died after a few weeks of normal use.
Electronics Bay
Cover removed, showing the internals. Front of the microwave is on the left.
Timer
Closeup of the timer unit. Cheap & nasty.
Magnetron
Magnetron removed from the oven. Antenna is on the top, cooling fins visible in the center. White conector at the bottom is the filament terminals.
Magnetron Chokes
Chokes on the magnetron’s filament connections. These prevent microwave energy from feeding back into the electronics bay through the connections.
Magnetron Assembly
Magnetron cooling fins, tube & magnets removed from the frame.
Magnetron Tube
Bare magnetron tube.
Power Input Board
This PCB does some rudimentary power conditioning, power resistors are in series with the live feed to the power trasformer, to prevent huge power up surge. When the transformer energizes the relay, which is in parallel with the resistors, switches them out a fraction of a second after, providing full power to the transformer.
Standard RFI choke & capacitor at the top of the board, with the input resistor.
Transformer
Power transformer to supply the magnetron with high voltage.
Power output is ~2kV at ~0.5A. Pair of spade terminals are the low voltage filament winding.
Capacitor
HV Capacitor. This along with the diode form a voltage doubler, to provide the magnetron with ~4kV DC.
Diode
HV diode stack.
Fuse Element
Internals of the HV fuse. Rated for ~0.75A at 5kV. The fuse element is barely visible attached to the end of the spring. Connects between the transformer & the capacitor.
Cooling Fan
Cooling fan for the magnetron. Drive is cheap shaded pole motor.
Fan Motor
Fan motor. Basic 240v shaded pole induction type.
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