Sharp R-1405 Service Manual page 16

R-1405
R-1406
PROCEDURE
LETTER
(HIGH VOLTAGES ARE PRESENT AT THE HIGH VOLTAGE TERMINAL, SO DO NOT ATTEMPT TO
MEASURE THE FILAMENT AND HIGH VOLTAGE.)
C HIGH VOLTAGE RECTIFIER TEST
1. Disconnect the power supply cord, and then remove outer case.
2. Open the door and block it open.
3. Discharge high voltage capacitor.
4. Isolate the rectifier from the circuit. Using the highest ohm scale of the meter, read the resistance across
5. Reconnect all leads removed from components during testing.
6. Reinstall the outer case (cabinet).
7. Reconnect the power supply cord after the outer case is installed.
8. Run the oven and check all functions.
NOTE: Be sure to use an ohmmeter that will supply a forward bias voltage of more than 6.3 volts.
D HIGH VOLTAGE CAPACITOR TEST
1. Disconnect the power supply cord, and then remove outer case.
2. Open the door and block it open.
3. Discharge high voltage capacitor.
4. If the capacitor is open, no high voltage will be available to the magnetron. Disconnect input leads and
5. Reconnect all leads removed from components during testing.
6. Reinstall the outer case (cabinet).
7. Reconnect the power supply cord after the outer case is installed.
8. Run the oven and check all functions.
E CAVITY THERMAL CUT-OUT TEST
1. Disconnect the power supply cord, and then remove outer case.
2. Open the door and block it open.
3. Discharge high voltage capacitor.
4. A continuity check across the thermal cut-out terminals should indicate a closed circuit unless the
5. Reconnect all leads removed from components during testing.
6. Reinstall the outer case (cabinet).
7. Reconnect the power supply cord after the outer case is installed.
8. Run the oven and check all functions.
MAGNETRON TEMPERATURE FUSE TEST
1. Disconnect the power supply cord, and then remove outer case.
2. Open the door and block it open.
3. Discharge high voltage capacitor.
4. A continuity check across the temperature fuse terminals should indicate a closed circuit. If the
5. Reconnect all leads removed from components during testing.
TEST PROCEDURES
the terminals and observe, reverse the leads to the rectifier terminals and observe meter reading. If a
short is indicated in both directions, or if an infinite resistance is read in both directions, the rectifier
is probably defective and should be replaced.
check for short or open between the terminals using an ohmmeter.
Checking with a high ohm scale, if the high voltage capacitor is normal, the meter will indicate continuity
for a short time and should indicate an open circuit once the capacitor is charged. If the above is not
the case, check the capacitor with an ohmmeter to see if it is shorted between either of the terminals
and case. If it is shorted, replace the capacitor.
temperature of the thermal cut-out reaches approximately 293½F(145½C).
An open thermal cut-out indicates overheating of the oven, exchange the oven thermal cut-out and
check inside of oven cavity and for improper setting of cooking time or operation of control unit. Check
for restricted air flow through the vent holes of the oven cavity, especially the cooling fan and air guide.
temperature of the magnetron reaches approximately 302½F(150½C), the temperature fuse opens. An
open temperature fuse indicates overheating of the magnetron. Check for restricted air flow to the
magnetron, especially the cooling fan air guide.
COMPONENT TEST
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