Sharp R-480J Service Manual page 13

PROCEDURE
LETTER
B. Continuity check must be carried out with measuring instrument which is set to the highest resistance
range.
C. A normal capacitor shows continuity for a short time (kick) and then a resistance of about 10MΩ after
it has been charged.
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 NOISE FILTER TEST
CARRY OUT 3D CHECKS.
Disconnect the leads from the terminals of the noise filter.
Using an ohmmeter, check between the terminals as de-
scribed in the following table.
MEASURING POINT
Between N and L
Between terminal N and WHITE
Between terminal L and RED
If incorrect readings are obtained, replace the noise filter unit.
CARRY OUT 4R CHECKS.
G 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 table below.
CARRY OUT 4R CHECKS.
Parts Name
Thermal cut-out 145˚C
If incorrect readings are obtained, replace the thermal cut-out.
An open circuit thermal cut-out 145˚C (MAGNETRON) indicates that the magnetron has over-
heated, 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 145˚C (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 time or failure of the
control panel.
TEST PROCEDURES
COMPONENT TEST
Table: Terminal Connection of Switch
COM to NO
Open circuit
Short circuit
INDICATION OF OHMMETER
Open circuit
Short circuit
Short circuit
Table: Thermal cut-out Test
Temperature of "ON"
condition (closed circuit) (˚C)
This is not resetable type.
11
COM to NC COM; Common terminal
Short circuit NO;
Open circuit NC;
N
NOISE SUPPRESSION COIL
LINE CROSS CAPACITOR
0.0022µ/AC 250V
WHT
Temperature of "OFF" Indication of ohmmeter
condition (open circuit) (˚C) (When room temperature
is approx. 20˚C)
Above 145˚C Closed circuit.
R-480J
Normally open terminal
Normally close terminal
L
FUSE
F10A
0.068µ/AC250V
0.0022µ/AC 250V
RED