Read Sharp R-770AM Service Manual online
1
770AM -
WARNING TO SERVICE PERSONNEL
Microwave ovens contain circuitry capable of producing very high voltage and current. Contact with following
parts will result in electrocution:-
parts will result in electrocution:-
High voltage capacitor, High voltage transformer, Magnetron, High voltage rectifier assembly, High voltage
harness.
harness.
REMEMBER TO CHECK 3D
1) Disconnect the supply.
2) Door opened, and wedged open.
3) Discharge high voltage capacitor.
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.
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.
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:-
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.
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 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%) and push the start key. When the one (1) minute has elapsed
(timer at zero) carefully check that the water is now hot.
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%) and push the start key. When the one (1) minute has elapsed
(timer at zero) carefully check that the water is now hot.
AFTER REPAIR REMEMBER TO CHECK 4R
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.
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.
be checked and microwave leakage test carried out.
IMPORTANT: If the oven becomes inoperative because of a blown fuse F8A in the 1st latch switch -
monitor switch circuit, check the 1st latch switch and monitor switch before replacing the fuse F8A.
monitor switch circuit, check the 1st latch switch and monitor switch before replacing the fuse F8A.
WARNING
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