Servicing - Sharp R-310B Service Manual

R-310B
FAN MOTOR
The fan motor drives a blade which draws external cool air.
This cool air is directed through the air vanes surrounding
the magnetron and cools the magnetron. This air is
channeled through the oven cavity to remove steam and
vapors given off from the heating foods. It is then ex-
Microwave ovens contain circuitry capable of producing very high voltage and current, contact with following parts
of the high voltage circuit will result in electrocution. High voltage capacitor, Power 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 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 trans-
former.
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.
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.

SERVICING

WARNING TO SERVICE PERSONNEL
TROUBLESHOOTING GUIDE
6
hausted through the exhausting air vents at the oven
cavity
NOISE FILTER
The noise filter prevents the radio frequency interference
that might flow back in the power circuit.
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 power level to HIGH. And set the
microwave timer for two (2) minutes. 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.
IMPORTANT: If the oven becomes inoperative because
of a blown fuse M8A in the 1st. latch switch
- 2nd. latch switch - monitor switch - moni-
tor resistor circuit, check the 1st. latch
switch, 2nd. latch switch, monitor switch
and monitor resistor before replacing the
fuse M8A.