Sharp R-4A68, Service Manual

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R-4A68
12
PROCEDURE
LETTER
COMPONENT TEST
TEST PROCEDURES (CONT'D)
perform the Key unit test (Procedure L) to determine if control unit is faulty.
2-1 In connection with pads.
a) When touching the pads, a certain group of pads do not produce a signal.
b) When touching the pads, no pads produce a signal.
2-2 In connection with indicators
a) At a certain digit, all or some segments do not light up.
b) At a certain digit, brightness is low.
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.
K KEY UNIT TEST
If the display fails to clear when the STOP/CLEAR pad is depressed, first verify the flat ribbon is marking
good contact, verify that the door sensing switch (stop switch) operates properly; that is the contacts are
closed when the door is closed and open when the door is open. If the door sensing switch (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 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.
G12
G11
G10
G 9
G 8 G 7 G 6 G 5 G 4 G 3 G 2 G 1
KEY UNIT
5 4 3 2 1
0 9 8 7 6
POWER
LEVEL
INSTANT
COOK
START
CLOCK
Pasta
Vegetable
STOP
CLEAR
Steaks
/Chops
Minced
Meat
Dinner
Plate
( FROZEN
FOOD)
AUTO
START
Chicken
Pieces
Beverage
Dinner
Plate
( SNACKS &
REHEAT)
Jacket
Potato
Fresh
Veg.
Casseroles
Rice
L RELAY TEST
CARRY OUT 3D CHECKS.
Remove the outer case and check the voltage between Pin Nos. 3 and 5 of the 3 pin connector (A) on the
control unit with an A.C. voltmeter.
The meter should indicate 220 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