R-7N76(W)M
R-7N76(B)M
9
TROUBLESHOOTING GUIDE
When troubleshooting the microwave oven, it is helpful to follow the Sequence of Operation in performing the checks. Many
of the possible causes of trouble will require that a specific test be performed. These tests are given a procedure letter which
will be found in the “Test Procedure” section.
IMPORTANT: If the oven becomes inoperative because of a blown fuse M8A in the 1st latch switch - monitor switch - monitor
resistor circuit, check the 1st latch switch, monitor switch and monitor resistor before replacing the fuse M8A.
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.
SERVICING
WARNING TO SERVICE PERSONNEL
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 assembly, High voltage harness.
REMEMBER TO CHECK 3D
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
with the use of an insulated screwdriver.
Sharp recommend that wherever possible fault-finding is
carried out with the supply disconnected. It may, in some
cases, be necessary to connect the supply after the outer
case has been removed, in this event carry out 3D checks
and then disconnect the leads to the primary of the high
voltage transformer. Ensure that these leads remain
isolated from other components and the oven chassis.
(Use insulation tape if necessary.) When the testing is
completed carry out 3D checks and reconnect the leads
to the primary of the high voltage transformer.
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.
Microwave ovens should not be run empty. 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 two (2) minutes. And set
the power level to HIGH (100%) and push the start key.
When the two minutes has elapsed (timer at zero) care-
fully check that the water is now hot. If the water remains
cold carry out 3D checks and re-examine the connections
to the component being tested.
