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[10] Procedure J: TOUCH CONTROL PANEL ASSEMBLY TEST
The touch control panel consists of circuits including semiconductors such as LSI, ICs, etc. Therefore, unlike conventional mic rowave
ovens, proper maintenance cannot be performed with only a voltmeter and ohmmeter. In this service manual, the touch control pan el
assembly is divided into two units, Control Unit and Key Unit, and also the Control Unit is divided into two units, CPU Unit an d Power
Unit, and troubleshooting by unit replacement is described according to the symptoms indicated.
ovens, proper maintenance cannot be performed with only a voltmeter and ohmmeter. In this service manual, the touch control pan el
assembly is divided into two units, Control Unit and Key Unit, and also the Control Unit is divided into two units, CPU Unit an d 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 switch unit. Replace the switch unit.
a) When touching the Pads, a certain Pad produces no signal at all.
b) When touching the Pads, sometimes a Pad produces no signal.
c) When rotating the TIMER/WEIGHT knob, the cooking time or the weight can not be input.
2. Control Unit.
The following symptoms indicate a defective control unit. Before replacing the control unit, perform the Key unit test ([11] Procedure K)
to determine if control unit is faulty.
1) In connection with buttons.
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) 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.
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.
[11] Procedure K: KEY UNIT (MEMBRANE SWITCH) TEST
If the display fails to clear when the STOP/CLEAR pad is depressed, first verify the flat ribbon cable is making good contact, ve rify
that the 2nd. interlock relay control switch operates properly; that is the contacts are closed when the door is clo sed and open when
the door is open. If the 2nd. interlock relay control switch is good, disconnect the flat ribbon cable that connects the key uni t to the
control unit and make sure the 2nd. interlock relay control switch is closed (either close the door or short the 2nd. interlock relay control
switch connector). Use the key unit matrix indicated on the control panel schematic and place a jumper wire between the pins th at
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 keypad is at fault.
that the 2nd. interlock relay control switch operates properly; that is the contacts are closed when the door is clo sed and open when
the door is open. If the 2nd. interlock relay control switch is good, disconnect the flat ribbon cable that connects the key uni t to the
control unit and make sure the 2nd. interlock relay control switch is closed (either close the door or short the 2nd. interlock relay control
switch connector). Use the key unit matrix indicated on the control panel schematic and place a jumper wire between the pins th at
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 keypad is at fault.
R-291(K)M
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