Sharp KB-5121KS Service Manual page 16

KB-5121KS/K/W
PROCEDURE
LETTER
4) Reconnect all leads removed from components during testing.
5) Re-install the covers.
6) Reconnect the power source after the outer case is installed.
7) Run the oven and check all functions.
B KEYBOARD UNIT TEST
1. Disconnect the power source, and then disassemble as per "COOK TOP/MICROWAVE DRAWER
DISASSEMBLY" page 32.
2. Open the drawer and block it open.
3. Discharge high voltage capacitor.
4. If the display fails to clear when the STOP/CLEAR pad is depressed, first verify the wire harness and
connectors are making good contact between the control unit and the keyboard, verify that the door
sensing switch operates properly; that is the contacts are closed when the door is closed and open
when the door is open.
5. Remove the old keyboard unit and install the new keyboed unit (as the normal keyboard unit).
6. Reconnect the wire harness to the keyboard unit.
7. If the control unit responds by clearing with a beep when the stop/clear pad is touched, the old keyboard
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 keyboed unit is at fault.
8. Reconnect all leads removed from components during testing.
9. Re-install the covers.
10.Reconnect the power source after the outer case is installed.
11.Run the oven and check all functions.
C RELAY TEST
1. Disconnect the power source, and then disassemble as per "COOK TOP/MICROWAVE DRAWER
DISASSEMBLY" page 32.
2. Open the drawer and block it open.
3. Discharge high voltage capacitor.
4. Disconnect the leads to the primary of the power transformer.
5. Ensure that these leads remain isolated from other components and oven chassis by using insulation tape.
6. After that procedure, re-connect the power supply cord.
7. Remove the covers and check voltage between Pin Nos. 1 and 3 of the 2 pin connector (CN-B) on the
power unit with an A.C. voltmeter.
The meter should indicate 116 or 120 volts, if not check oven circuit.
RY1 and RY2 Relay Test
These relays are operated by D.C. voltage
Check voltage at the relay coil with a D.C. voltmeter during the microwave cooking operation.
DC. voltage indicated .................... Defective relay.
DC. voltage not indicated ............... Check diode which is connected to the relay coil. If diode is good,
TEST PROCEDURES
RELAY SYMBOL OPERATIONAL VOLTAGE
RY1 Approx. 18V D.C.
RY2 Approx. 18V D.C.
RY3 Approx. 18V D.C.
RY4 Approx. 18V D.C.
RY5 Approx. 24V D.C.
RY6 Approx. 24V D.C.
RY7 Approx. 24V D.C.
RY8 Approx. 24V D.C.
RY9 Approx. 24V D.C.
RY10 Approx. 24V D.C.
RY11 Approx. 24V D.C.
RY-B Approx. 24V D.C.
RY-C Approx. 24V D.C.
COMPONENT TEST
control unit is defective.
CONNECTED COMPONENTS
Oven lamp / Stirrer motor
Power transformer
Oven common relay
Top heater
Fan motor (Microwave)
Fan motor (Oven)
Oven lamp (Oven)
Door lock motor (Oven)
Convection motor
Warmer (Cook top)
Switching power supply
Bottom heater
Convection heater
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