Sharp R-733B, Service Manual

Page: 16 / 40

14 R-733 -
TEST PROCEDURES
PROCEDURE
LETTER COMPONENT TEST
F THERMAL CUT OUT TEST
CARRY OUT 3D CHECKS
Disconnect the leads from the terminals of the thermal cut-out. Then using an ohmmeter, make a
continuity test across the two terminals as described in the below.
CARRY OUT 4R CHECKS
Table: Thermal Cut-out Test
PARTS NAME THERMAL CUT-OUT THERMAL CUT-OUT
Condition 125
°
C (MAG) 160
°
C (OVEN)
Temperature of ”ON” condition This is not resetable type This is not resettable type
(closed circuit)
Temperature of ”OFF” condition
Above 125
°
C Above 160
°
C
(open circuit)
Indication of ohmmeter (When room
Closed circuit Closed circuit
temperature is approx. 20
°
C.)
If incorrect readings are obtained replace the thermal cut-out.
An open circuit thermal cut-out (MG) indicates that magnetron has overheated, this may be due to
restricted ventilation, cooling fan failure or a fault condition within the magnetron or HV circuit.
An open circuit thermal cut-out (OVEN) indicates that the foods in the oven may catch fire, this may be
due to over heating produced by improper setting of the cooking timer or failure of the control panel.
An open circuit thermal cut-out (GRILL) indicates that the oven cavity has overheated, this may be due
to no load operation.
CARRY OUT 3D CHECKS
If the fuse F1 F8A is blown when the door is opened, check the monitored latch switch and monitor
switch.
If the fuse F1 F8A is blown by incorrect door switching replace the defective switch(s) and the fuse F1
F8A
BLOWN FUSE F1 F8A
If the fuse F1 is blown, there could be a short in the asymmetric rectifier or there is a ground in wire
harness. A short in the asymmetric rectifier may have occured due to short or ground in H.V. rectifier,
magnetron, power transformer or H.V. wire. Check them and replace the defective parts or repair the
wire harness.
CARRY OUT 4R CHECKS
CAUTION: Only replace fuse with the correct value replacement.
CARRY OUT 3D CHECKS
If the fuse 15A is blown, there could be shorts or grounds in electrical parts or wire harness. Check them
and replace the defective parts or repair the wire harness.
CARRY OUT 4R CHECKS
CAUTION: Only replace fuse 15A with the correct value replacement
G BLOWN FUSE 15A F2
H BLOWN FUSE F8A F1