Sharp R-870B, Service Manual

Page: 19 / 48

R-870B
17
TEST PROCEDURES
PROCEDURE
LETTER COMPONENT TEST
(stop switch) is good, disconnect the flat ribbon cable that connects the key unit to the control unit and
make sure the door sensing switch is closed (either close the door or short the door sensing switch
connecter). 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 marking 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 a 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.
ARRY OUT 3D CHECKS.
Remove the outer case and check voltage between Pin No. 1 of the 3 pin connector (A) and the
common terminal of the relay RY6 on the control unit with an A.C. voltmeter.
The meter should indicate 220 volts, if not check oven circuit.
Relay Test
Check voltage at the relay coil with a D.C. voltmeter during the microwave cooking operation, grill
operation, convection operation or mix 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. 24.0V D.C. Convection motor
RY2 Approx. 24.0V D.C. High voltage transformer
RY3 Approx. 24.0V D.C. Grill heaters (Top)
RY4 Approx. 24.0V D.C. Bottom heater
RY5 Approx. 24.0V D.C. Fan motor
RY6 Approx. 24.0V D.C. Oven lamp / Turntable motor
CARRY OUT 4R CHECKS.
P RELAY TEST
Q 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 input circuit
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.
CARRY OUT 4R CHECKS.
5
4
3
2 1
0 9 8 7 6
G 8 G 7 G 6 G 5 G 4 G 3 G 2 G 1
G12
G11
G10
G 9
PIZZA
HELP
BAKE
ROAST
EASY
DEFROST
(AUTO COOK)
GRILL
INSTANT
COOK/
START
CONVEC
POWER
LEVEL
STEAM
MENU
CRISPY
SNACK
REHEAT
DISH
SLOW
COOK
GRILL
REHEAT MIX
STOP/
CLEAR
RICE
COOK