Sharp R-4A56, Service Manual

Page: 17 / 40

R-4A56
15
TEST PROCEDURES (CONT'D)
PROCEDURE
LETTER
COMPONENT TEST
N 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.
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.
RY2
S1
3
1
US:RED,CD:GRY
GE:BLK,AS:BRN
D32
(TAB1)
(COM.)
(TAB2)
(H.V.)
(J1)
17
VRS1
T1
D31
(H.V.) POWER O.L.,F.M.,T.T.M.,
CN–A
RY1
5 7 3 1
a
b
d
c
STEPS OCCURANCE CAUSE OR CORRECTION
1 The rated voltage is not applied to POWER Check supply voltage and oven main unit.
terminal of CPU connector (CN-A).
2 The rated voltage is applied to primary side Low voltage transformer or secondary circuit defective.
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)