R420LW
8 – 5
f) A certain group of indicators do not light up.
g) The figure of all digits flicker.
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.
3. If the Key unit or the Control unit is defective.
1) Disconnect the power supply cord, and then remove outer case.
2) Open the door and block it open.
3) Discharge high voltage capacitor.
4) Replace the Control unit assembly.
5) Reconnect all leads removed from components during testing.
6) Re-install the outer case (cabinet).
7) Reconnect the power supply cord after the outer case is installed.
8) Run the oven and check all functions.
4. When testing is completed,
1) Disconnect the power supply cord and then remove outer case.
2) Open the door and block it open.
3) Discharge high voltage capacitor.
4) Reconnect all leads removed from components during testing.
5) Re-install the outer case (cabinet).
6) Reconnect the power supply cord after the outer case is installed.
7) Run the oven and check all functions.
[12] Procedure K: KEY UNIT TEST
1. Disconnect the power supply cord, and then remove outer case.
2. Open the door 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 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 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 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.
5. Reconnect all leads removed from components during
testing.
6. Reinstall the outer case (cabinet).
7. Reconnect the power supply cord after the outer case is
installed.
8. Run the oven and check all functions.
[13] Procedure L: RELAY TEST
1. Disconnect the power supply cord, and then remove outer case.
2. Open the door 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 outer case and check voltage between the cabinet side terminal of the relay RY1 and the lower side terminal of the relay RY2 on the
control unit with an A.C. voltmeter.
The meter should indicate 120 volts, if not check oven circuit.
G5
G4
G3
G8
G10
G11
G13
G7
G6
G9
G12
G2
G1
4
1
7
2
5
8
0
6
3
9
KEEP WARM
PLUS
POWER
LEVEL
STEAKS/
CHOPS
SENSOR
REHEAT
BONE-IN
POULTRY
BONELESS
POULTRY
GROUND
MEAT
(DEFROST)
GROUND
MEAT
(SENSOR COOK)
FISH
SEAFOOD
FRESH
VEGETABLES
FROZEN
VEGETABLES
FROZEN ROLLS/
MUFFINS
FROZZEN
ENTREES
CUSTOM
HELP
POPCORN
CHICKEN
BREAST
BEVERAGE
RICE
HOT
WATER
BAKED
POTATOES
START
MINUTE PLUS
TIMER
CLOCK
STOP
CLEAR
FRESH ROLLS/
MUFFIN