Sharp R-450H, Service Manual

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12
R-450H
TEST PROCEDURES
PROCEDURE
LETTER
COMPONENT TEST
c) Only one indicator does not light.
d) The corresponding segments of all digits do not light up; or they continue to light up.
e) Wrong figure appears.
f) A certain group of indicators do not light up.
g) The figure of all digits flicker.
2-3 Other possible troubles caused by defective control unit.
a) Buzzer does not sound or continues to sound.
b) Clock does not operate properly.
c) Cooking is not possible.
L KEY UNIT TEST
If the display fails to clear when the STOP/CLEAR pad is depressed, first verify the flat ribbon cable
is making good contact, verify that the door 2nd. interlock relay control switch operates properly; that
is the contacts are closed when the door is closed and open when the door is open. If the 2nd. interlock
relay control switch is good, disconnect the flat ribbon cable that connects the key unit to the control
unit and make sure the 2nd. interlock relay control switch is closed (either close the door or short the
2nd. interlock relay control switch connector). Use the key unit matrix indicated on the control panel
schematic and place a jumper wire between the pins that correspond to the STOP/CLEAR pad
making momentary contact. If the control unit responds by clearing with a beep the key unit is faulty
and must be replaced. If the control unit does not respond, it is faulty and must be replaced.
If a specific pad does not respond, the above method may be used (after clearing the control unit) to
determine if the control unit or key pad is at fault.
CARRY OUT 3D CHECKS.
M RELAY TEST
Remove the outer case and check voltage between Pin No 1 of the 2-pin connector (A) and the
common terminal of the relay RY1 on the power unit with an A.C. voltmeter. The meter should indicate
230 - 240 volts, if not check oven circuit.
RY1 and RY2 Relay Test
These relays are operated by D.C. voltage.
Check voltage at the relay coil with a D.C. voltmeter during the microwave cooking operation.
DC. voltage indicated ............... Defective relay.
DC. voltage not indicated ......... Check diode which is connected to the relay coil. If diode is good,
control unit is defective.
RELAY SYMBOL OPERATIONAL VOLTAGE CONNECTED COMPONENTS
RY1 APPROX. 25.0V D.C. Oven lamp / Turntable motor / Cooling fan motor
RY2 APPROX. 24.0V D.C. Power transformer
CARRY OUT 4R CHECKS.
N 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.
G 1 G 2 G 3 G 4 G 5 G 6 G 7 G 8
G 9
G10
G11
G12
G13
G14
5
0
4
9
3
8
2
7
1
6
DINNER
PLATE
VEGETABLES
EASY
DEFROST
PASTA
MEAL
PIZZA
EXPRESS
MEAL
FROZEN
DINNER
PIE
EXPRESS
COOK
CASSEROLE
SOUP
INSTANT COOK
START
LESS
TIMER
POWER
LEVEL
RICE/
PASTA
CLOCK
MORE
BEVERAGE
EXPRESS
DEFROST
STOP
CLEAR
HELP