Sharp R-677W Service Manual page 19

PROCEDURE
LETTER
O 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.
STEPS
1
2
3
4
NOTE: *At the time of these repairs, make a
visual inspection of the varistor for
burning damage and examine the
transformer with a tester for the pres-
ence of layer short-circuit (check pri-
mary coil resistance). If any abnor-
mal condition is detected, replace the
defective parts.
CARRY OUT 4R CHECKS.
TEST PROCEDURES
OCCURRENCE
The rated AC voltage is not present at
POWER terminal of CPU connector (CN-A).
The rated AC voltage is present at primary
side of low voltage transformer.
Only pattern at "a" is broken.
Pattern at "a" and "b" are broken.
R-677 - 19
...
CONT
COMPONENT TEST
CAUSE OR CORRECTION
Check supply voltage and oven power cord.
Low voltage transformer or secondary circuit defective.
Check and repair.
*Insert jumper wire J1 and solder.
(CARRY OUT 3D CHECKS BEFORE REPAIR)
*Insert the coil RCILF2003YAZZ between "c" and "d".
(CARRY OUT 3D CHECKS BEFORE REPAIR)
CN - A
T1
d
VRS1
a
b
c
1