R-2398G. Complete - Sharp Home Appliance Service Manual (repair manual). Page 10

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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 proce-
dure letter which will be found in the “Test Procedure”
section.

IMPORTANT: If the oven becomes inoperative because

of a blown fuse F6.3A in the 1st. latch
switch - monitor switch - monitor resistor
circuit, check the 1st. latch switch, monitor
switch and  monitor resistor before replac-
ing the fuse F6.3A.

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 con-
nection 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.

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

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 fuse, High
voltage harness.

1) Reconnect all leads removed from components dur-

ing 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 power level to HIGH (100%) and set the
microwave timer for two (2) minutes. And push the start
key. When the two minutes has elapsed (timer at zero)
carefully 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.