Sharp R-671(B) Service Manual page 17

TEST PROCEDURES
PROCEDURE
LETTER
D. A short-circuited capacitor shows continuity all the time.
E. An open capacitor constantly shows a resistance about 10 MΩ because of its internal 10MΩ
resistance.
F. When the internal wire is opened in the high voltage capacitor shows an infinite resistance.
G. The resistance across all the terminals and the chassis must be infinite when the capacitor is
normal.
If incorrect reading are obtained, the high voltage capacitor must be replaced.
CARRY OUT 4R CHECKS.
E SWITCH TEST
CARRY OUT 3D CHECKS.
Isolate the switch to be tested and using an ohmmeter check between the terminals as described in
the following table.
Plunger Operation
Released
Depressed
If incorrect readings are obtained, make the necessary switch adjustment or replace the switch.
CARRY OUT 4R CHECKS.
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.
Parts Name
Thermal cut-out 145˚C
Thermal cut-out 150˚C
If incorrect readings are obtained, replace the thermal cut-out.
An open circuit thermal cut-out TC1 (HVT) indicates that the high voltage transforner has overheated,
this may be due to resistricted ventilation, cooling fan failure or a fault condition within the high voltage
transformer or HV. circuit.
An open circuit thermal cut-out TC2 (OVEN) indicates that the food in the oven cavity may catch fire,
this may be due to over heating produced by improper setting of the cooking timer or failure of the
control panel.
CARRY OUT 4R CHECKS.
G BLOWN FUSE 15A (F1)
CARRY OUT 3D CHECKS.
If the fuse 15A is blown, there could be a 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:
H BLOWN FUSE F8A (F2)
CARRY OUT 3D CHECKS.
If the fuse F8A (F2) is blown when the door is opened, check the primary latch switch, monitor switch
and monitor resistor.
...
CONT
Table: Terminal Connection of Switch
COM to NO
Open circuit
Short circuit
Temperature of "ON"
condition (closed circuit).
(˚C)
Cuts back in at 115˚C.
Cuts back in at 130˚C.
15A with the correct value replacement.
Only replace fuse
R-671 - 16
COMPONENT TEST
COM to NC
COM; Common terminal,
Short circuit NO;
NC;
Open circuit
Table: Thermal Cut-out Test
Temperature of "OFF"
condition (open circuit).
(˚C)
Above 145˚C
Above 150˚C
Normally open terminal
Normally close terminal
Indication of ohmmeter
(When room temperature
is approx. 20˚C.)
Closed circuit
Closed circuit