Sharp R-450C, Service Manual

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12
R-450C
TEST PROCEDURES
PROCEDURE
LETTER
COMPONENT TEST
units, Control Unit and Key Unit, and also the Control Unit is divided into two units, CPU Unit and
Power Unit, and troubleshooting by unit replacement is described according to the symptoms
indicated.
1. Key Unit. Note: Check key unit ribbon connection before replacement.
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 Unit.
The following symptoms indicate a defective control unit. Before replacing the control unit, perform
the Key unit test (Procedure M) 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.
M 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 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 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.
5
4
3 2 1
0 9 8 7 6
BEVERAGE
POWER
LEVEL
FROZEN
DINNER
MEAT CLOCK TIMER
HELP
LESS
DINNER
PLATE
RICE/
PASTA
PASTA
MEAL
EASY
DEFROST
STOP
CLEAR
VEGETABLES
INSTANT
COOK
START
G 8
G 9
G10
G11
G12
G13
G14
G 7 G 6 G 5 G 4 G 3 G 2 G 1
SOUP CASSEROLE
PIE PIZZA
MORE