Sharp R-4H55 Service Manual page 9

RdX55
RdX55B
TURNTABLE MOTOR
The turntable motor drives the turntable roller assembly to
neled through the oven cavity to remove steam and
vapors
given off from the heating foods. It is then exhausted
rotate the turntable. through the exhausting air vents at the oven cavity.
FAN MOTOR
The fan motor drives a blade which draws external cool air.
NOISE FILTER (For New Zealand Model R-4X55)
The noise filter prevents the radio frequency interference
This cool air is directed through the air vanes surrounding
that might flow back in the power circuit.
the magnetron and cools the magnetron. This air is chan-
servicing
WARNING TO SERVICE PERSONNEL
Microwave ovens contain circuitry capable of producing very high voltage and current, contact with any part of the
high voltage circuit will result in electrocution.
REMEMBER TO CHECK 3D
REMEMBER TO
CHECK*
1) Disconnect the supply.
2) Door opened, and wedged open.
3) Discharge high voltage capacitor.
1) Reconnect all leads removed from components dur-
ing testing.
2) Replace the outer case (cabinet).
3) Reconnect the supply.
WARNING AGAINST THE CHARGE OF THE 4) Run the oven. Check all functions.
HIGH-VOLTAGE CAPACITOR
The high-voltage capacitor remains charged about
Microwave ovens should not be run empty. To test for
60 seconds after the oven has been switched off.
the presence of microwave energy within a cavity,
Wait for 60 seconds and then short-circuit the con-
place a cup of cold water on the oven turntable, close
nection of the high-voltage capacitor (that is, of the
the door and set the microwave timer for two (2) min-
connecting lead of the high-voltage rectifier) against
utes. Set the power level to HIGH and push the START
the chassis with the use of an insulated screwdriver.
button. When the two minutes has elapsed (timer at
zero) carefully check that the water is now hot. If the
Sharp recommend that wherever possible fault-finding
water remains cold carry out 3D checks and re-exam-
is carried out with the supply disconnected. It may in,
ine the connections to the component being tested.
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 pri-
mary of the power 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 power transformer.
When all service work is completed, and the oven is fully assembled, the microwave power output should be
checked and microwave reakage test carried out
TROUBLESHOOTING GUIDE
When troubleshooting the microwave oven, it is helpful
IMPORTANT: If the oven becomes inoperative because of a
to follow the Sequence of Operation in performing the
blown fuse M8A in the upper latch switch -
checks. Many of the possible causes of trouble will re-
lower latch switch - monitor switch - monitor
quire that a specific test be per-formed. These tests are
resistor circuit, check the upper latch switch,
given a procedure letter which will be found in the "Test
lower latch switch, monitor switch and moni-
Proceduresection.
tor resistor before replacing the fuse M8A.
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