Servicing - Sharp R-3A54 Service Manual

R-3A54
R-3E54
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 electrocuition.
REMEMBER TO CHECK 3D
1) Disconnect the supply.
2) Door opened, and wedged open.
3) Discharge high voltage capacitor.
I-
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 con-
necting lead of the high-voltage rectifier)
against the chassis with the use of an insu-
lated screwdriver.
Sharp recommend
that wherever possible
fault-finding is carried out with the supply discon-
nected. It may in, some cases, be necessary to
connect the supply after the outer case has been
removed, in this event carry out 3lJ checks and then
disconnect the leads to the primary 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.
REMEMBER TO CHECK $lJ
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. Set the power level to
HIGH and push the START button. When the two
minutes has elapsed (timer at zero) carefully check
that the water is now hot. If the water remains cold
carry out 3lJ checks and re-examine the con-
nections to the component being tested.
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
helpfull to follow the Sequence of Operation in per-
forming 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 be-
cause of a blown fuse (M8A) in the
1 st latch switch - 2nd latch switch -
monitor switch
- monitor resisitor cir-
cu-it, check the 1st latch switch, 2nd
latch switch, monitor switch and
monitor resistor before replacing the
fuse (M8A).