Sharp R-231NW Service Manual - Page 13

Troubleshooting Guide

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CHAPTER 7. TROUBLESHOOTING GUIDE R-231NW Never touch any part in the circuit with your hand or an uninsulated tool while the power supply is connected. 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 procedure letter which will be found in the "Test Procedure "section. IMPORTANT: If the oven becomes inoperative because of a blown monitor fuse, check the monitor switch, primary interlock relay (RY2), door sensing switch and secondary interlock switch before replacing the monitor fuse. If monitor fuse is replaced, the monitor switch must also be replaced. Use part FFSBA026WRKZ as an assembly. IMPORTANT: Whenever troubleshooting is performed with the power supply cord disconnected. It may in, some cases, be necessary to connect the power supply cord after the outer case has been removed, in this event, 1) Disconnect the power supply cord, and then remove outer case. 2) Open the door and block it open. 3) Discharge high voltage capacitor. 4) Disconnect the leads to the primary of the power transformer. 5) Ensure that the leads remain isolated from other components and oven chassis by using insulation tape. 6) After that procedure, reconnect the power supply cord. When the testing is completed, 1) Disconnect the power supply cord, and then remove outer case. 2) Open the door and block it open. 3) Discharge high voltage capacitor. 4) Reconnect the leads to the primary of the power transformer. 5) Reinstall the outer case (cabinet). 6) Reconnect the power supply cord after the outer case is installed. 7) Run the oven and check all functions. [1] TROUBLESHOOTING CHART TTEST PROCEDURE RE CK A B C D E F F G H RE RE CK J/L CK CK CK K N M I POSSIBLE CASE AND DEFECTIVE PARTS SHORT IN POWER CORD SHORT OR OPENED WIRING MAGNETRON POWER TRANSFORMER H.V. RECTIFIER ASSEMBLY HIGH VOLTAGE CAPACITOR TEMPERATURE FUSE (OVEN) or THERMAL CUT-OUT (OVEN) PRIMARY INTERLOCK SYSTEM SECONDARY INTERLOCK SWIT MONITOR SWITCH MONITOR FUSE OVEN LAMP COOLING FAN MOTOR TURNTABLE MOTOR CONTROL UNIT or RELAY WRONG OPERATION LOW VOLTAGE DIRTY OVEN CAVITY KEY UNIT (MEMBRAINE SWITCH FOIL PATTERN ON PWB. DEFROST NOISE FILTER CONDITION PROBLEM Home fuse blows when power cord is plugged into wall receptacle. Monitor fuse blows when power cord is plugged into wall receptacle. OFF CONDITION Any letters or indicators do not appear in display when power cord is first plugged into wall outlet. Display does not operate properly when STOP/CLEAR key is touched. (Buzzer should sound and time of day should appear in display.) Monitor fuse blows when the door is opened. Fan motor does not operate. (All other electric components function.) Oven lamp does not light at all. (All other electric components function.) Turntable motor does not operate. (All other electric components function.) Oven does not go into cook cycle when START pad is touched COOKING CONDITION Oven seems to be operating but little or no heat is produced in oven load. (Food incompletely cooked or not cooked at all at end of cook cycle.) Oven goes into a cook cycle but extremely uneven heating is produced in oven load (food). Oven does not cook properly when programmed for Cooking 50% mode. (Operates properly on Cooking Power 100% mode.) Oven lamp, turntable motor and fan motor do not operate. Oven goes into DEFROST but food is not defrosted well. 7 - 1

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R-231NW
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 speci
fi
c test be performed. These tests are given a procedure letter which will be found in
the “Test Procedure “section.
IMPORTANT:
If the oven becomes inoperative because of a blown monitor fuse, check the monitor switch, primary interlock relay (RY2), door
sensing switch and secondary interlock switch before replacing the monitor fuse. If monitor fuse is replaced, the monitor switch must
also be replaced. Use part FFSBA026WRKZ as an assembly.
7 - 1
CHAPTER 7. TROUBLESHOOTING GUIDE
Never touch any part in the circuit with your hand or an uninsulated tool while the power supply is connected.
IMPORTANT:
Whenever troubleshooting is performed with the power supply
cord disconnected. It may in, some cases, be necessary to
connect the power supply cord after the outer case has been
removed, in this event,
1)
Disconnect the power supply cord, and then remove outer
case.
2) Open the door and block it open.
3) Discharge high voltage capacitor.
4) Disconnect the leads to the primary of the power transformer.
5) Ensure that the leads remain isolated from other components
and oven chassis by using insulation tape.
6) After that procedure, reconnect the power supply cord.
When the testing is completed,
1
)
Disconnect the power supply cord, and then remove outer case.
2) Open the door and block it open.
3) Discharge high voltage capacitor.
4) Reconnect the leads to the primary of the power transformer.
5) Reinstall the outer case (cabinet).
6) Reconnect the power supply cord after the outer case is
installed.
7) Run the oven and check all functions.
[1] TROUBLESHOOTING CHART
RE CK A
B
C
D
E
F
F
G
H RE RE CK J/L CK CK CK K
N
M
I
POSSIBLE CASE
AND DEFECTIVE PARTS
D
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CONDITION
PROBLEM
OFF
CONDITION
TTEST PROCEDURE
COOKING
CONDITION
Home fuse blows when power cord is plugged
into wall receptacle.
Monitor fuse blows when power cord is plugged
into wall receptacle.
Any letters or indicators do not appear in display
when power cord is first plugged into wall outlet.
Display does not operate properly when
STOP/CLEAR key is touched. (Buzzer should
sound and time of day should appear in display.)
Monitor fuse blows when the door is opened.
Fan motor does not operate. (All other electric
components function.)
Oven lamp does not light at all. (All other electric
components function.)
Turntable motor does not operate. (All other
electric components function.)
Oven does not go into cook cycle when START
pad is touched
Oven seems to be operating but little or no heat
is produced in oven load. (Food incompletely
cooked or not cooked at all at end of cook cycle.)
Oven goes into a cook cycle but extremely
uneven heating is produced in oven load (food).
Oven does not cook properly when programmed
for Cooking 50% mode. (Operates properly on
Cooking Power 100% mode.)
Oven lamp, turntable motor and fan motor do not
operate.
Oven goes into DEFROST but food is not
defrosted well.