Sharp R-961 (W) - Page 21

TEST PROCEDURES
PROCEDURE
LETTER COMPONENT TEST
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 below.
CARRY OUT 4R CHECKS.
Table: Thermal Cut-out Test
i! Temperature of Temperature of Indication of ohmmeter
condition “ON" "OFF" condition (When room temperature
Parts Name (closed circuit). {open circuit). is approx. 20°C.)
Closed circuit
If incorrect readings are obtained, replace the thermal cut-out.
An open circuit thermal cut-out (GRILL) TC1 indicates that the oven cavity has overheated, this may be
due to no load operation.
An open circuit thermal cut-out (MG) TC2 indicates that the magnetron has overheated, this may be due
to resistricted ventilation, cooling fan failure.
An
open
circuit
thermal
cut-out
(CONV.)
TC3
indicates
that
the
convection
fan
motor
winding
has
overheated,
this
may
be
due
to
resisted
ventilation
or
locked
cooling
fan
or
locked
convection
fan
motor.
An
open
circuit
thermal
cut-out
(FAN)
TC4
indicates
that
the
fan
motor
winding
has
overheated,
this
may
be due to blocked ventilation or locked cooling.
H TOR WINDIN T
CARRY OUT 3D CHECKS.
Disconnect the leads from the motor. Using an ohmmeter, check the resistance between the two
terminals as described in the table below.
If incorrect readings are obtained, replace the motor.
Table: Resistance of Motor
CARRY OUT 4R CHECKS.
NOISE FILTER TEST
CARRY OUT 3D CHECKS.
Disconnect the leads from the terminals of noise filter.
Using an ohmmeter, check between the terminals as
described in the following table.
o——}+— R2 Cy RED
F8A R1: 10 MQ + 20%
R2 : 680 kQ = 20%
Cx + 20% Cy + 20%
1.0mH 0.22uF 4700pF
MEASURING POINTS INDICATION OF OHMMETER
Between N and L Approx. 680 kQ
Between terminal N and WHITE Short circuit
Between terminal L and RED Short circuit
If incorrect readings are absorbed, replace the noise filter unit.
CARRY OUT 4R CHECKS.
R-961 - 19