Sharp R-3A56, Service Manual

Page: 17 / 40

R-3A56
15
TEST PROCEDURES (CONT'D)
PROCEDURE
LETTER
COMPONENT TEST
M PROCEDURES TO BE TAKEN WHEN THE FOIL PATTERN ON THE PRINTED WIRING
BOARD(PWB) IS OPEN.
To protect the electronic circuits, this model is provided with a fine foil pattern added to the primary on
the PWB, this foil pattern acts as a fuse. If the foil pattern is open, follow the troubleshooting guide given
below for repair.
Problem: POWER ON, indicator does not light up.
CARRY OUT 3D CHECKS.
NOTE: At the time of these repairs, make a visual
inspection of the varistor for burning damage
and examine the transformer with tester for
the presence of layer short-circuit (check
primary coil resistance). If any abnormal
condition is detected, replace the defective
parts.
CARRY OUT 4R CHECKS.
(VRS2)
VRS1
(J1) CN - A
POWER
5 1
RY1
6
P
2
RY2
T1
(RY3)
(J2+)
a
b
d c
N NOISE FILTER TEST
If incorrect readings are obtained, replace the noise filter unit.
CARRY OUT 4R CHECKS.
CARRY OUT 3D CHECKS.
Disconnect the leads from the terminals of the noise
filter. Using an ohmmeter, check between the terminals
as described in the following table.
L (min) Cx
±
20% Cy
±
20%
1.0 mH 0.068
µ
F 0.0022
µ
F
MEASURING POINT INDICATION OF OHMMETER
Between N and L Open circuit
Between terminal N and WHITE Short circuit
Between terminal L and RED Short circuit
N
L
C
L
L
C
WHT
RED
X
Y
STEPS OCCURANCE CAUSE OR CORRECTION
1 The rated AC voltage is not present at Check supply voltage and oven power cord.
POWER terminal of CPU connector (CN-A)
2 The rated AC voltage is present at primary Low voltage transformer or secondary circuit defective.
side of low voltage transformer. Check and repair.
3 Only pattern at "a" is broken. *Insert jumper wire J1 and solder.
(CARRY OUT 3D CHECKS BEFORE REPAIR)
4 Pattern at "a" and "b" are broken. *Insert the coil RCILF2003YAZZ between "c" and "d".
(CARRY OUT 3D CHECKS BEFORE REPAIR)