Sharp R-7A55 - Page 21

19
R-7A55(W)/(B)
R-7E45(W)/(B)
TEST PROCEDURES (CONT'D)
PROCEDURE
LETTER
COMPONENT TEST
BOAD(PWB) IS OPEN
N PROCEDURES TO BE TAKEN WHEN THE FOIL PATTERN ON THE PRINTED WIRIN ING
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.
STEPS OCCURANCE CAUSE OR CORRECTION
1 The rated AC voltage is not present at
POWER terminal of CPU connector (CN-A)
Check supply voltage and oven power cord.
2 The rated AC voltage is present at primary
side of low voltage transformer.
Low voltage transformer or secondary circuit defective.
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)
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
D24D22
D25
21
20
19
E Q24
B
D23
18
J1
VRS1
POWER
CONV M FAN M
5 7
13
1356
(R94)
ZD1
D20
S1P
S2
8
a
d
c
b