R-252M (serv.man2) - Sharp Home Appliance Service Manual (repair manual). Page 7

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R-252M   7
When troubleshooting the microwave oven, it is helpful to
follow the Sequence of Operation in performing the checks.
Many of the possible causes of trouble will require that a
specific test be performed. These tests are given a proce-
dure letter which will be found in the “Test Procedure”
section.
IMPORTANT: If the oven becomes inoperative because
of a blown fuse. Check the monitored latch
switch and monitor switch before replac-
ing the F1 fuse.
   TROUBLESHOOTING GUIDE
CONDITION
PROBLEM
A
B
C
D
E
E E
F G
H
I
I
J
K
L
L
M
Home fuse blows when power cord 
is plugged into wall outlet.
Fuse F1   blows when power cord 
is plugged into wall outlet. (Timer 
off)
All letters and indicators do not 
appear in display when power cord 
is first plugged into wall outlet.
Display does not operate properly 
when Stop/Clear pad is touched. 
(Buzzer should sound and "  ;  " or 
time of day should appear in display.
Oven lamp does not light, when in 
operation. 
Fan motor does not operate. 
Turntable motor does not operate. 
Oven or electrical parts does not 
stop when cooking time is 0 or 
Stop/Clear pad is touched. 
Oven seems to be operating but 
little or no heat is produced in oven 
load. (Microwave power level is set 
at HIGH.)
Oven does not operate properly during 
the variable cooking condition except 
100% (HIGH) cooking condition.
Oven goes into cook cycle but 
shuts down before end of cooking 
cycle.
Oven stops as soon as the oven is 
started.
Fan motor, oven lamp and 
turntable motor do not operate at 
the same time.
OFF
CONDITION
COOKING
CONDITION
TEST PROCEDURE
POSSIBLE CAUSE
AND
DEFECTIVE PARTS
MAGNETRON
HIGH VOLTAGE  TRANSFORMER
H.V. RECTIFIER
HIGH VOLTAGE CAPACITOR
MONITORED LATCH SWITCH
STOP SWITCH
MONITOR SWITCH
THERMAL CUT-OUT 125
ß
C
FUSE F1
NOISE FILTER
FAN MOTOR
TURNTABLE MOTOR
POWER SUPPLY CORD
OVEN LAMP OR SOCKET
SHORTED WIRE HARNESS
OPENED WIRE HARNESS
MIS-ADJUSTMENT SWITCHES
NO POWER AT WALL OUTLET
HVT THERMOSTAT
CONTROL UNIT
KEY UNIT
RELAY RY1
RELAY RY3
FOIL PATTERN ON P.W.B.
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