To Service Personnel - Sharp R-4A52 Service Manual

R-4A52
R-4E52
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 4R
1) Disconnect the supply.
2) Door opened, and wedged open.
3) Discharge high voltage capacitor.
WARNING AGAlNST THE CHARGE OF THE
HIGH-VOLTAGE CAPACITOR
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.
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 con-
necting lead of the high-voltage rectifier)
against the chassis with the use of an insu-
lated screwdriver.
Microwave ovens shouid 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. And set the timer for two (2) minutes. 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
Sharp
recommend that wherever possible
the connections to the component being tested.
faultifinding is carried out with the supply.discon-
netted.
It may in, some cases, be necessary to
connect the supply after the outer case has been
removed, in this event carry out 30 checks and then
disconnect the leads to the pnmary 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 ofihe power transformer.
When all service work is completed, and the oven is fully assembled, the microwave power output should
be checked and a microwave leakage test carried out.
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 wiil be found in the
"Test Procedure"section.
IMPORTANT: If the oven becomes inoperative be-
cause of a blown fuse E (M8A) in the
upper latch switch - lower latch
switch - monitor switch - monitor
resisitor circuit, check the lower latch
switch, monitor switch and monitor
resistor before replacing the fuse E
(M8A).
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