R-205WM - Sharp Home Appliance Service Manual (repair manual). Page 2

R-205M - 2

Microwave ovens should not be used without a load.   To test for the presence of microwave energy within a cavity,
place a cup of cold water on the oven turntable, close the door and set the microwave timer for one (1) minute, set the
power level to HIGH (100%).  When the one (1) minute has elapsed (timer at zero) carefully check that the water is now
hot.

1) Reconnect all leads removed from components during testing.
2) Replace the outer case (cabinet).
3) Reconnect the supply.
4) Run the oven. Check all functions.

When all service work is completed, and the oven is fully assembled, the microwave power output should be checked
and microwave leakage test carried out.

IMPORTANT: If the oven becomes inoperative because of a blown fuse F1 in the monitored latch switch - monitor

switch circuit, check the monitored latch switch and monitor switch before replacing the fuse F1.

Sharp recommend that wherever possible, fault-finding is carried out with the supply disconnected.  In some
cases, it may be necessary to connect the supply with  the cover removed to carry out fault investigation in the
control circuitry.  In such cases, the high voltage circuit should be disabled as described below to reduce the
hazards:-

•

Carry out 3D checks (see above).

•

Disconnect the supply leads from the high voltage transformer, making a note of the polarity.  Insulate the
connectors, ensuring they are positioned away from the transformer and fastened there.

•

Connect any relevant test equipment e.g. voltmeter.

•

Reconnect the oven to the supply, then close the door.

•

Note the results of the test, taking care to keep clear of the operational oven.

•

Carry out 3D checks (see above).

•

Reconnect the leads to the transformer.  Take care to observe correct polarity.

•

Carry out 4R checks (see below).

Microwave ovens contain circuitry capable of producing very high voltage and current. Contact with following parts
will result in electrocution:-
High voltage capacitor, High voltage transformer, Magnetron, High voltage rectifier, High voltage wires.

1) Disconnect the supply.
2) Door opened, and wedged open.
3) Discharge high voltage capacitor.

WARNING AGAINST THE CHARGE OF THE HIGH-VOLTAGE CAPACITOR

The high-voltage capacitor remains charged about 60 seconds after the oven has been switched off. Wait for 60
seconds and then short-circuit the connection of the high-voltage capacitor (that is, of the connecting lead of the
high-voltage rectifier) against the chassis using a screwdriver with an insulated handle.