Sharp R-895(AL)M Service Manual page 22

PROCEDURE
LETTER
M TOUCH CONTROL PANEL ASSEMBLY TEST
The control panel consists of circuits including semiconductors such as LSI, ICs, etc. Therefore, unlike
conventional microwave ovens, proper maintenance can not be performed with only a voltmeter and
ohmmeter.
In this service manual, the control panel assembly is divided into two units, Control Unit and Key Unit,
and also the Control unit is divided into two units, CPU unit and Power unit, and troubleshooting by
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 Panel
The following symptoms indicate a defective control unit. Before replacing the control unit perform
the key unit test (Procedure N) 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 up.
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.
d) Proper temperature measurement is not obtained.
N KEY UNIT TEST
If the display fails to clear when the STOP/CLEAR pad is depressed, first verify the ribbon cable is
making good contact, verify that the stop switch operates properly; that is the contacts are closed when
the door is closed and open when the door is open. If the stop switch is good, disconnect the flat ribbon
cable that connects the key unit to the control unit and make sure the stop 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 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 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.
CARRY OUT 4R CHECKS.
TEST PROCEDURES
COMPONENT TEST
G 8 G 7
Crispy
Pie/
G 9 Crumb
Quiche
Foods
G10
Desserts PIZZA
Chicken
G11
Quarters
MORE
DUAL
Whole
G12 CONV. /
Poultry
GRILL
R-895M - 17
G 6 G 5 G 4
Rice/ Crispy Ready
Potatoes
Pasta Meals
Roast
Italian Roast
Beef/
Dish Pork
Lamp
START
Roast
Poultry AUTO MINUTE
LESS
STOP
Indian Meat
Dish
CLEAR Joint
G 3 G 2 G 1
10sec. 1min. 10min.
Chinese
GRILL BREAKFAST
Dish
POWER
LEVEL
UP DOWN
KITCHEN TIMER
CONV
info
CLOCK SET (˚C)