Read Sharp R-891M Service Manual online
7
891M -
COMPONENT TEST
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
Switch Unit, and also the Control Unit is divided into two units, Display Unit and Power Unit, and
troubleshooting by unit replacement is described according to the symptoms indicated.
1. Switch Unit. Note : Check switch unit lead wire harness connection before replacement.
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
Switch Unit, and also the Control Unit is divided into two units, Display Unit and Power Unit, and
troubleshooting by unit replacement is described according to the symptoms indicated.
1. Switch Unit. Note : Check switch unit lead wire harness connection before replacement.
The following symptoms indicate a defective switch unit. Replace the switch unit.
a) When touching the buttons, a certain button produces no signal at all.
b) When touching a number button, two figures or more are displayed.
c) When touching the buttons, sometimes a button produces no signal.
a) When touching the buttons, a certain button produces no signal at all.
b) When touching a number button, two figures or more are displayed.
c) When touching the buttons, sometimes a button produces no signal.
2. Control Unit
The following symptoms indicate a defective control unit. Before replacing the control unit (power
unit and/or display unit), perform the Switch unit test (Procedure K) to determine if control unit is
faulty.
unit and/or display unit), perform the Switch unit test (Procedure K) to determine if control unit is
faulty.
2-1 In connection with buttons.
a) When touching the buttons, a certain group of buttons do not produce a signal.
b) When touching the buttons, no buttons produce a signal.
b) When touching the buttons, no buttons produce a signal.
2-2 In connection with indicators
a) At a certain digit, all or some dots do not light up.
b) At a certain digit, brightness is low.
c) Only one indicator does not light.
d) The corresponding dots 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 dots 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.
TOUCH CONTROL PANEL ASSEMBLY TEST
SWITCH UNIT TEST
If the display fails to clear when the STOP/CLEAR button
is depressed, first verify the lead wire harness 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 lead wire harness that connects the switch
unit to the display unit and make sure the door sensing
switch is closed (either close the door or short the door
sensing switch connecter). Use the Switch unit matrix
indicated on the switch unit circuit and place a jumper wire
between the pins that correspond to the STOP/CLEAR
button making momentary contact. If the display unit
responds by clearing with a beep the switch unit is faulty
and must be replaced. If the display unit does not
respond, it is a faulty and must be replaced. If a specific
button does not respond, the above method may be used
(after clearing the display unit) to determine if the display
unit or switch unit is at fault.
is depressed, first verify the lead wire harness 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 lead wire harness that connects the switch
unit to the display unit and make sure the door sensing
switch is closed (either close the door or short the door
sensing switch connecter). Use the Switch unit matrix
indicated on the switch unit circuit and place a jumper wire
between the pins that correspond to the STOP/CLEAR
button making momentary contact. If the display unit
responds by clearing with a beep the switch unit is faulty
and must be replaced. If the display unit does not
respond, it is a faulty and must be replaced. If a specific
button does not respond, the above method may be used
(after clearing the display unit) to determine if the display
unit or switch unit is at fault.
G 8
G 9
G 7
G 6
G 5
G 4
G 3
G 2
G 1
SW16
SW12
SW8
7
8
9
START
AUTO MINUTE
DUAL
BOOK MARK
BREAKFAST
CONVECTION
MICROWAVE
GRILL
PIZZA
INDEX
2
3
4
SW15
SW19
05
SW20
SW11
SW7
1
SW3
SW2
SW1
6
SW4
SW14
SW18
SW10
SW6
SW13
SW17
SW9
SW5
STOP
CLEAR
TEST PROCEDURES
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