Read Sharp R-252M (serv.man2) Service Manual online
R-252M 12
The touch control panel consists of circuits including semiconductors such as LSI, ICs, etc.
Therefore, unlike conventional microwave ovens, proper maintenance cannot be performed with
only a voltmeter and ohmmeter.
In this service manual, the touch 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 unit replacement is described according to the symptoms indicated.
1. Key Unit
Therefore, unlike conventional microwave ovens, proper maintenance cannot be performed with
only a voltmeter and ohmmeter.
In this service manual, the touch 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 unit replacement is described according to the symptoms indicated.
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.
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. 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.
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.
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.
b) Clock does not operate properly.
c) Cooking is not possible.
TEST PROCEDURES
PROCEDURE
LETTER
COMPONENT 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
connecter). Use the Key unit matrix indicated on 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.
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
connecter). Use the Key unit matrix indicated on 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.
K
KEY UNIT TEST
1 min.
RICE /
PASTA
FRESH
FISH
FRESH
VEG.
MINCED
MEAT
CAKE
CANNED
FOOD
POWER
LEVEL
JACKET
POTATOES
BOILED
POTATOES
SPONGE
PUDDING
AUTO
DEFROST
LESS
g • oz
Kg • Lb
Kg / Lb
MORE
AUTO
COOK
TIMER
STOP/
CLEAR
10 sec.
10 min.
START
CLOCK
AUTO
MINUTE
AUTO
START
G12
G11
G10
G 9
G 1
G 2
G 3
G 4
G 5
G 6
G 7
G 8
J
CONTROL PANEL ASSEMBLY TEST
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