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Complete Microwave Oven Service Handbook

The Complete Microwave Oven Service Handbook
Operation, Maintenance, Troubleshooting and Repair

The complete, definitive eBook vocational course on commercial and residential microwave oven operation, maintenance and repair
Updated for 2012

Click here for more information about  You Can Fix Microwave Ovens--The Video

MICROTECH Glossary of Electronic & Microwave Oven Related Terms
Copyright © 1989-2013 J. Carlton Gallawa . All Rights Reserved Worldwide
Excerpts from the book
The Complete Microwave Oven Service Handbook
and from the video
You Can Fix Your Microwave Oven, Plus VCR Know-How
Copyright ©, 1996-2013 by J. Carlton Gallawa

Click here to comment, suggest a correction or to submit a relevant term we have not defined.

AC VOLTAGE: An electric current that reverses its direction regularly and continually, thus it is
Alternating Current.
AMPERAGE: The strength of an electric current measured in amperes. One ampere is the amount of
current that flows through one ohm of resistance with one volt applied.
AMPLITUDE: The maximum instantaneous value of an alternating wave of voltage or current measured
from a reference line to either a maximum positive value or maximum negative value.
ANALOG: A variable that remains similar to another variable in proportional relationships over a
specified range.
ANODE: The positive electrode in an electrochemical device. In a magnetron tube, the anode is usually
the outer casting and is at ground potential.
ANODIZE: A process that electrolytically produces an insulating oxide film on a conducting surface.
ANTENNA PIN: See tuning stub.
BIAS: A DC voltage applied to the control electrode of an electronic device to establish the desired
operating point.
CAPACITANCE: The property of a capacitor that determines how much charge can be stored in it for a
given potential difference across its terminals. The basic unit is the farad. However, the small microfarad
unit is more commonly used: abbreviated MFD.
CATHODE: The general name for any negative electrode. In a magnetron tube, the cathode is centered
within the anode and at high negative voltage potential.
CAVITY RESONATOR: A space totally enclosed by a metallic conductor and supplied with energy in
such a way that it becomes a source of electromagnetic oscillations. In a microwave oven, the food
compartment is a resonant cavity
CHOKE: (1) An inductance (usually a coil) used in a circuit to impede the flow of pulsed DC or AC
without appreciably affecting the flow of DC. (2) A groove, channel, or other discontinuity that is
dimensioned so as to reflect guided electromagnetic waves of a certain frequency range.
CONVECTION: The transmission of heat by the mass movement of the heated air.
CORE: A magnetic material that affords an easy path for magnetic lines of flux.
CUMULATIVE EFFECT: Many exposures to small doses add up to a large dose.
CURRENT LIMITER: A protective device, used in some two-fold applications as a fuse, that is designed
to limit current flow in high-amperage circuits.
CYCLE: One complete positive and one complete negative alternation of a current or voltage.
DC VOLTAGE: An electric current that flows in one direction only, thus it is Direct Current.
DIELECTRIC: A material of poor conductivity that serves as an insulator, usually in reference to the
insulating material between the plates of a capacitor. The dielectric separates the metal plates electrically,
stores an electric charge, and undergoes polarization when subjected to an electric field.
DIFFERENCE OF POTENTIAL: The voltage existing between two points. If a circuit is established
between the two points, a flow of electrons will result.
DIRECTLY HEATED CATHODE: A wire or filament that is designed to emit electrons when an
electric current flows through it. The current heats the filament to the point where electrons are emitted.
DUMMY LOAD: A device used at the end of a waveguide to convert transmitted energy into heat so no
energy is radiated outward or reflected back.
DUTY CYCLE: In a magnetron tube: The ratio of oscillating time to total time.
ELECTRODE: The terminal at which electricity passes from one medium into another, such as in a
humidity sensor unit where the current leaves or returns to the semi-conducting ceramic compound.
ELECTROMAGNETIC RADIATION: The process in which waves of electromagnetic energy are sent
out into space.
ELECTROMAGNETIC WAVE: A wave of energy propagated by the combined interaction of electric
and magnetic fields that are traveling at right angles to each other, and to the direction of travel.
ELECTRON: A high-speed, negatively-charged particle that revolves around the nucleus, and forms a
part, of all atoms.
ELECTROSTATIC: Pertaining to electricity at rest or to stationary electricity (static electricity), such as
a static charge on an object.
FERRITE: A ferric oxide material that has both magnetic properties and a high resistance to current
flow. The high electrical resistivity makes any current losses extremely low at high frequencies.
FET: Field-effect transistor.
FILAMENT: A resistance wire or ribbon that, in a magnetron tube, is also the cathode. When an electric
current flows through it, the filament heats up to a temperature by which electrons are liberated, thus the
filament produces free (or floating) electrons.
FLUX: In electrical or electromagnetic devices, a general term used to designate collectively all the
electric or magnetic lines of force in a given region.
FREQUENCY: The number of times a wave makes one full cycle in one second of time. Usually
expressed in hertz (Hz).
FULL- WAVE RECTIFIER: A circuit that uses both positive and negative alternations of an alternating
current to produce a direct current.
GROUND: Zero potential with respect to the ground or earth. A metallic connection with the earth is
used to establish ground potential, and to provide a common return to a point of zero potential. When
connected to a properly grounded and polarized circuit, the chassis of a microwave oven is at ground
HALF- WAVE RECTIFIER: A circuit that uses only ½ of each cycle to change AC to pulsating DC.
HARMONIC FREQUENCIES: Integral multiples of a primary frequency.
HEATER: See filament.
HEATSINK: A metal device that is clamped onto a heat-sensitive component for the purpose of diverting
and dissipating soldering iron heat.
HENRY: The basic unit of inductance.
HERTZ: Cycles per second.
IC: Integrated Circuit. An interconnected network of electrochemical elements integrated into a tiny
electronic circuit that performs at least one, and usually more, logic functions.
IMPEDANCE: A combination of resistance and reactance that offers opposition to the flow of current in
a circuit. Impedance is usually expressed in ohms.
INDUCTANCE: The property of a circuit that causes a magnetic field to be produced which tends to
oppose any change in the existing current flow. The basic unit of inductance is the henry.
INDUCTION: The act or process by which a voltage is produced by the relative motion of a magnetic
field across a conductor. Or, the process by which a magnetic field is produced by the variance of an
electric current through a conductor.
INFINITE OHMS: An incalculably high amount of electrical resistance—essentially an open circuit.
INSULATOR: An implement having high electrical resistance, used for supporting, surrounding, or
separating conductors so as to prevent undesired current flow between the conductors or to other objects.
INTERFACE CIRCUITRY: Serves to link the otherwise incompatible high-impedance circuits of the
microprocessor and the high-potential circuits of external components.
IONIZING: The dislodging of orbital electrons from atoms, creating electrically charged, highly
unstable, and chemically reactive atoms, called ions, which are damaging to living cells.
LAYER SHORT: A condition in a transformer in which two adjacent windings come into abnormal
contact with each other through the insulating layer.
LC CIRCUIT: A circuit containing inductive reactance and capacitive reactance.
LCD: Liquid Crystal Display. A digital display which utilizes a liquid crystal material to form digits and
characters without generating any light. The liquid crystal material separates and is sealed-in by two
sheets of glass, one of which has character-forming segments etched into it and serves as the viewing
side. When voltage is applied to the electrodes that extend from each of the etched segments, the liquid
adjacent to the segments changes tone (usually darkens), thus forming visible characters.
LED: Light-Emitting Diode. A semi-conductor diode that efficiently converts electric signals into light,
and thus glows when current passes through it. In microwave ovens, LEDs are generally used for control
panel displays and indicators.
LOAD: An object or device that consumes electrical energy, and thus changes the energy into another
form. Food products change microwave energy into heat energy.
MEG OHM: One million ohms.
MICRO: A prefix meaning one-millionth.
MICROFARAD: One millionth of a farad; abbreviated MFD.
MICROPROCESSOR: A microprocessor incorporates various computer functions such as memory,
calculation, data processing, and control into a tiny silicone chip. The microprocessor receives input and
generates output signals in a sequence of logic, which is either externally programmed or internally
MILLI: A prefix meaning 1/1000.
MILLIWATT: 1/1000 of a watt of electricity.
MODULATION/DEMODULATION: Modulation is the ability to impress intelligence upon a
transmission medium. A transmission medium may be described as radio waves, light or infrared beams,
wire lines, sound, or other communication systems. The characteristics (intelligence) of one waveform are
impressed onto a second waveform by varying the frequency, amplitude, phase, or other characteristics of
the second waveform. Demodulation is the removal or recovery of the intelligence from the medium.
MOSFET: Metal oxide semiconductor field-effect transistor.
NEGATIVE CHARGE: An electrical medium which has an excess of electrons, thus having the ability to
repel electrons.
NEGATIVE TEMPERATURE COEFFICIENT: A factor that expresses the amount of reduction in the
value of a quantity relative to ambient temperature. For example, a given decrease in a resistance for each
degree of increase in temperature.
OHM: The basic unit of resistance. One volt will cause one ampere of current to flow through one ohm of
OPEN CIRCUIT: A circuit that does not provide a complete path for the flow of current.
OPTO-COUPLER: See photo-coupler.
PARALLEL CIRCUIT: Two or more electrical devices connected to the same pair of terminals so more
than one current path is available. Current flows through each device in the parallel circuit.
PHASE: The relationship in time and polarity between two waves. A phase difference results when one
wave leads or lags another.
PHOTO-COUPLER: An isolated coupling device which, when energized by an input, sends a signal to a
semiconductor switching device, such as an SCR.
POLARITY: The relative condition of being positive or negative with respect to a given potential.
POLARIZED RECEPTACLE: A receptacle designed to ensure that the neutral side of an AC line is
always connected to the neutral side of an appliance, such as a microwave oven.
POSITIVE CHARGE: An electrical medium that has become deficient in electrons, thus having the
ability to attract electrons.
POTENTIAL: The amount of charge held by a body as compared to another point or body. A difference
in voltage potential between two connected points results in current flow between the two points. The
difference in potential is measured in volts.
PROTONS: One of the fundamental particles of the nucleus of an atom and carries a unitary positive
RADIATION: The process of emitting radiant energy in the form of waves or particles.
RC CIRCUIT: A circuit having a resistance and a capacitance in series.
RESONANCE: The condition produced when the frequency of vibrations is the same as the natural
frequency of a cavity. The cavity is sympathetic to the frequency; thus, the vibrations reinforce each
RESONANT CIRCUIT: (explained in detail in part 3) A coil and capacitor connected in parallel form a
capacitive-inductive resonant circuit. Energy supplied to the circuit will charge up the capacitor. When
the energy supply is removed, the capacitor discharges through the coil. Current flow through the coil
causes a magnetic field to develop around coil. The magnetic field then collapses around the coil, selfinducing
a current flow in the opposite direction, which then charges the capacitor in the opposite
polarity. Consequently, the capacitor discharges again, starting the process all over.
SCR: A semiconductor device that is controlled by a gate signal. Normally the SCR acts as an open
switch, but upon application of an appropriate gate signal to its gate terminal, the SCR instantly switches
to a conducting state, becoming as a closed switch.
SERIES CIRCUIT: An arrangement of electrical devices that are connected so that the total current must
flow through all the devices in order to complete the circuit.
SHORT CIRCUIT: A low resistance (usually zero ohms) connection across a voltage source or between
two points in a circuit that are of different electrical potential. A short circuit usually results in excessive
and possibly damaging current flow.
SOLENOID: An electromagnetic coil that contains a movable plunger.
STANDING WAVE: The distribution of waves in a reflective enclosure in which the waves coincide at
maximum and minimum points on a resultant wave that appears to stand still.
SUBSONIC: Sound waves beyond the lower limits of human audibility.
SYNTHESIZER: See Voice Synthesizer.
TERMINAL: (1) A point to which electrical connections can be made. (2) The electrical input or output
of a circuit or component.
TRIGGER: A short pulse, either positive or negative, which can be used to cause an electrical function to
TUNING STUB: A rod, screw, or post of conductive material that projects into a waveguide for one or
more of the following purposes: impedance matching, producing desired phase relationships, or to
minimize reflected energy.
ULTRASONIC: Pertaining to sound waves having a frequency that is generally above the limits of
human audibility.
VOICE SYNTHESIZER: An instrument that simulates speech by digital control. The synthesizer
assembles and digitizes the various elements of a dialect, so the appropriate inflections and other speech
characteristics of any language can be simulated.
VOLT: The unit of electrical potential (electromotive force or electrical pressure). One volt is the pressure
required to send one ampere of current through one ohm of resistance.
VOLTAGE: Voltage is the force (or pressure) that causes current to flow through a conductor. The
voltage of a circuit is the greatest effective difference of potential between any two conductors of a
VOLTAGE DROP: Ratio of voltage (or electrical pressure) lost (or dropped) across a specified load as a
result of forcing current flow through that load.
WATT: The practical unit of electric power. In a DC circuit, one watt of power is used when one ampere
of current flows through a resistance of one ohm.
WAVEGUIDE: A rectangular, circular, or elliptical hollow metal tube designed to transport
electromagnetic energy through its interior from one point to another.
WAVELENGTH: (1) The distance in space occupied by one cycle of an electromagnetic wave at any
given instant. (2) The distance a wave travels during one cycle.

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Disclaimer: The author assumes no liability for any incidental, consequential or other liability from the use of this information. All risks and damages, incidental or otherwise, arising from the use or misuse of the information contained herein are entirely the responsibility of the user. Although careful precaution has been taken in the preparation of this material, we assume no responsibility for omissions or errors.
Back | Home Page | Microwave Oven FiX Finder | Instructional CD-ROM | Copyright Information

Copyright © 1989-2013 J. Carlton Gallawa . All Rights Reserved Worldwide