Sharp R-84ST Service Manual page 18

PROCEDURE
LETTER
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
If incorrect readings are obtained, replace the thermal cut-out.
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 (OVEN) TC1 indicates that the oven cavity has overheated, this may be
due to no load operation.
H MOTOR WINDING TEST
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.
CARRY OUT 4R CHECKS
I NOISE FILTER TEST
CARRY OUT 3D CHECKS
Disconnect the leads from the terminals of
noise filter.
Using an ohmmeter, check between the ter-
minals as described in the following table.
If incorrect readings are absorbed, replace the noise filter unit.
CARRY OUT 4R CHECKS
TEST PROCEDURES
COMPONENT TEST
Parts Name
Thermal cut-out
150˚C TC1
Thermal cut-out
125˚C TC2
Motors
Fan motor
Turntable motor
Convection fan motor
MEASURING POINTS
Between N and L
Between terminal N and WHITE
Between terminal L and RED
R-84ST -
Table: Thermal Cut-out Test
Temperature of Temperature of
"ON" condition "OFF" condition
(closed circuit). (open circuit).
(˚C)
Below 130˚C Above 150˚C
This is not resetable Above 125˚C
type
Table: Resistance of Motor
Approximately 292Ω
Approximately 14.5kΩ
Approximately 290 Ω
L (min)
1.0mH
18
Indication of
ohmmeter
(When room
(˚C) temperature is
approx. 20˚C.)
Closed circuit
Closed circuit
Resistance
20A
L
L
Cx
N L
F8A
R1: 10 MΩ ± 20%
R2 : 680 kΩ ± 20%
Cx ± 20% Cy ± 20%
0.22µF
INDICATION OF OHMMETER
Approx. 680 kΩ
Short circuit
Short circuit
WHT
R1
RED
R2 Cy
R1: 10M ohm ± 20%
R2: 680k ohm ± 20%
4700pF