Sharp R-3A56, Service Manual

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R-3A56
14
TEST PROCEDURES (CONT'D)
PROCEDURE
LETTER
COMPONENT TEST
1. Key Unit
The following symptoms indicate a defective key unit. Replace the key unit.
a) When touching the pads, a certain pad produces no signal at all.
b) When touching a number pad, two figures or more are displayed.
c) When touching the pads, sometimes a pad produces no signal.
2. Control Panel
The following symptoms indicate a defective control unit. Replacing the control unit.
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 problems 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 ribbon is making 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 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 stop switch connecter).
Use the key unit matrix indicated on the control panel schematic and place a iumper 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 spe-
cific 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.
KEY UNIT
STOP
CLEAR
POWER
LEVEL
G 12
G 11
G 10
G 9
G 8
G 7 G 6
G 5
G 4 G 3
G 2
G 1
LESS
MORE
1
2 3 4
5
6 7 8 9 0
AUTO
COOK
AUTO
START
CLOCK
EASY
DEFROST
Reheat
Beverage
INSTANT
COOK
START
Frozen
Dinner
Reheat
Pie
4 X
3 X 2 X
Reheat
Pizza
Pasta
Meal
L RELAY TEST
CARRY OUT 3D CHECKS.
Remove the outer case and check 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 indicat 240 volts, if not check oven circuit.
RY1 and RY2 Relay Test
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. 26.0 V.D.C. Oven lamp/ Turntable motor/ Cooling fan motor
RY2 Approx. 25.5 V.D.C. Power transformer
CARRY OUT 4R CHECKS.