R990K(W)
7 – 1
R990K(W)
Service Manual
CHAPTER 7.
TROUBLESHOOTING GUIDE
[1] FOREWORD
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 Pro-
cedure”section.
IMPORTANT
:
If the oven becomes inoperative because of a blown fuse F10A in the
upper latch switch - lower latch switch - monitor switch circuit, check
the upper latch switch, lower latch switch and monitor switch before
replacing the fuse F10A.
[2] CHART
MAGNETRON
POWER
TRANSFORMER
H.V.
RECTIFIER
ASSEMBLY
HIGH
VOLTAGE
CAPACITOR
LATCH
AND
STOP
SWITCHES
MONITOR
SWITCH
DAMPER
SWITCH
MAIN
FUSE
TEMPERATURE
FUSE
150C
THERMAL
CUT-OUT
CONVECTION
HEATER
THERMISTOR
FAN
MOTOR
TURNTABLE
MOTOR
CONVECTION
MOTOR
DAMPER
MOTOR
HIGH
VOLTAGE
FUSE
TOUCH
CONTROL
PANEL
KEY
UNIT
RELAY
(RY-1)
RELAY
(RY-2)
RELAY
(RY-3)
RELAY
(RY-4)
RELAY
(RY-5)
RELAY
(RY-6)
FOIL
PATERN
ON
P.W.B.
AH.
SENSOR
OVEN
LAMP
OR
SOCKET
O
PENED
O
R
SHORTED
WIRE
HARNESS
WALL
OUTLET
LOW
POWER
SUPPLY
VOLTAGE
SHORTED
POWER
CORD
NOISE
FILTER
CK = Check / RE = Replace
OFF
CONDITION
A B C D E E E F G G H I J J J J K M N O O O O O O P Q
RE CKCK CK RE
L
COOKING
CONDITION
(MICROWAVE)
PROBLEM
CONDITION
TEST PROCEDURE
POSSIBLE
CAUSE
AND
DEFECTIVE
PARTS
(AH. SENSOR)
(CONVECTION)
Home fuse blows when power
supply cord is plugged into wall
outlet.
Fuse M8A blows when power
cord is plugged into wall outlet.
Oven lamp does not light with
door opened.
Oven lamp does not light at all
Cooling fan motor does not operate.
The oven stops after1 minute.
Oven lamp light, but turntable
motor does not operate.
Oven does not go into a cook cycle,
when START pad is touched.
Function of variable cooking does
not operate properly except
HIGH power.
Oven is in the sensor cook-ing
condition but AH sensor does not
end 1st. stage or does not stop
cooking cycle or the oven stops
soon.
CONV
indicator
lights,
but
heating element does not heat.
Temperature in the oven cavity is
lower or higher than preset.
Convection cycle runs 1 minute
then the oven shuts down.
Convection cycle runs 3 min-
utes then the oven shuts down.
Extremely uneven heating is
produced in oven load (food).
Display does not show anything
when power cord is first plugged
into wall outlet.
Display does not operate properly
when STOP/ CLEAR pad is
touched. (The time of day should
appear on the display with beep
sound during normal condition.)
Low or no power is produced
during microwave cooking (The
food is heated incom-pletely or
not heated at all)
Summary of Contents for Carousel R-990K
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