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1. Precaution
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1. Precaution
Follow these special safety precautions. Although the microwave oven is completely safe during ordinary use,
repair work can be extremely hazardous due to possible exposure to microwave radiation, as well as potentially
lethal high voltages and currents.
1-1 Safety precautions ( )
1. All repairs should be done in accordance with the 13. Design Alteration Warning: Use exact replacement
procedures described in this manual. This product parts only, i.e.,only those that are specified in
complies with Federal Performance Standard 21 thedrawings and parts lists of this manual. This
CFR is especially important for the Interlock switches,
2. Microwave emission check should be performed to described above. Never alter or add to the
prior to servicing if the oven is operative. mechanical or electrical design of the MWO.
Any design changes or additions will void the
3. If the oven operates with the door open :Instruct
manufacturer's warranty. Always unplug the unit's
the user not to operate the oven and contact
AC power cord from the AC power source before
the manufacturer and the center for devices and
attempting to remove or reinstall any component or
radiological health immediately.
assembly.
4. Notify the Central Service Center if the microwave
14. Never defeat any of the B+ voltage interlocks. Do not
leakage exceeds 5 mW/cm2.
apply AC power to the unit (or any of its assemblies)
5. Check all grounds. unless all solid-state heat sinks are correctly
6. Do not power the MWO from a "2-prong" AC cord. installed.
Be sure that all of the built-in protective devices are 15. Some semiconductor ("solid state") devices
replaced. Restore any missing protective shields. are easily damaged by static electricity. Such
7. When reinstalling the chassis and its assemblies, components are called Electrostatically Sensitive
be sure to restore all protective devices, including: Devices (ESDs). Examples include integrated
nonmetallic control knobs and compartment covers. circuits and field-effect transistors. Immediately
8. Make sure that there are no cabinet openings before handling any semiconductor components or
through which people --particularly children--might assemblies, drain the electrostatic charge from your
insert objects and contact dangerous voltages. body by touching a known earth ground.
Examples: Lamp hole,ventilation slots. 16. Always connect a test instrument's ground lead to
9. Inform the manufacturer of any oven foundto have the instrument chassis ground before connecting the
emission in excess of 5 mW/cm2 ,Make repairs to positive lead; always remove the instrument's ground
bring the unit into compliance at no cost to owner lead last.
and try to determine cause. Instruct owner not to use 17. When checking the continuity of the witches or
oven until it has been brought into compliance. transformer, always make sure that the power is
CENTRAL SERVICE CENTER OFF, and one of the lead wires is disconnected.
10. Service technicians should remove their watches 18. Components that are critical for safety are indicated
while repairing an MWO. in the circuit diagram by shading, or .
11. To avoid any possible radiation hazard,replace parts 19. Use replacement components that have the same
in accordance with the wiring diagram. Also, use ratings, especially for flame resistance and dielectric
only the exact replacements for the following parts: strength specifications. A replacement part that does
Primary and secondary interlock switches, interlock not have the same safety characteristics as the
monitor switch. original might create shock, fire or other hazards.
12. If the fuse is blown by the Interlock Monitor Switch: NOTE : Connect the oven to a 20A. When
Replace all of the following at the same time: connecting the oven to a 15A,make sure that circuit
Primary, door sensing switch and power relay, as breaker can operate.
well as the Interlock Monitor Switch. The correct
adjustment of these switches is described elsewhere
in this manual. Make sure that the fuse has the
correct rating for the particular model being repaired.
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1. Precaution
1-2 Special High Voltage Precautions
1. High Voltage Warning Do not attempt to measure any of H. V. Capacitor
the high voltages --this includes the filament voltage of the
magnetron. High voltage is present during any cook cycle.
Before touching any components or wiring, always unplug
the oven and discharge the high voltage capacitor (See
Figure 1-1)
2. The high-voltage capacitor remains charged about 30
seconds after disconnection. Short the negative terminal
of the high-voltage capacitor to to the oven chassis. (Use a
screwdriver.)
3. High voltage is maintained within specified limits by close-
tolerance, safety-related components and adjustments. If
the high voltage exceeds the specified limits, check each
of the special components.
H. V. Diode
Short
PRECAUTION
There exists HIGH VOLTAGE ELECTRICITY with high current capabilities in the circuits of the HIGH
VOLTAGE TRANSFORMER secondary and filament terminals. It is extremely dangerous to work on or
near these circuits with the oven energized.
DO NOT measure the voltage in the high voltage circuit including filament voltage of magnetron.
PRECAUTION
Servicemen should remove their watches whenever working close to or replacing the magnetron.
PRECAUTION
Never touch any circuit wiring with your hand nor with uninsulated tool during operation.
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