Panasonic Microwave oven NN-ST652WRUN, NN-ST652WRUK troubleshooting, Circuit diagram

DISASSEMBLY AND ADJUSTMENT
OUTER CASE REMOVAL
1) Disconnect the power supply cord from the outlet.
2) Remove the screws from the rear and alongside edges of the case.
The outer case must be moved backward to be lifted off.
POWER SUPPLY CORD
1) Remove the outer case.
2) Disconnect two terminals, and remove one screw of the earth terminal.
CAUTION: DISCHARGE THE HIGH VOLTAGE CAPACITOR BEFORE SERVICING

CONTROL PANEL ASSEMBLY

1) Disconnect the leadwire from the Timer motor

2) Remove the screws for securing the control panel.
3) Lift control panel ASS ’Y from the oven by the tab unhooked.

DOOR ASSEMBLY REMOVAL
1) Open the door.
CAUTION: Be careful not to damage Door by screwdriver.
3) Lift up and pull the door.
NOTE: 1. After replacing the door, be sure to check that the primary switch, monitor switch, and secondary switch operate normally.
2. After replacing the door, check for microwave energy leakage with a survey meter. Microwave energy must be below the limit of 5 mW/cm2. (with a 275 ml water load)
3. When mounting the door assembly to the oven assembly, be sure to adjust the door assembly parallel to the chassis. Also adjust so the door has no play between the inner door surface and oven frame assembly. If the door assembly is not mounted properly, microwaves may leak from the clearance between the door and the oven.

AIR GUIDE ASSEMBLY REMOVAL
1) Disconnect the leadwire from lamp, A.C Relay and monitor resistor and magnetron.
2) Remove the screw to the cavity.

MAGNETRON REMOVAL
1) Disconnect the leadwire from the high voltage transformer and high voltage capacitor.
2) Remove the air guide.
3) Carefully remove the mounting screws holding the magnetron and the wave-guide.
4) Remove the magnetron until the tube is clear from the wave-guide.

NOTE:
1. When removing the magnetron, make sure its dome does not hit any adjacent parts, or it may be damaged.

2. When replacing the magnetron, be sure to install the magnetron gasket in the correct position and be sure that the gasket is in good condition.
3. After replacing the magnetron, check for microwave leakage with a survey meter around the magnetron. Microwave energy must be below the limit of 5 mW/cm2. (With a 275 ml. water load).  Make sure that gasket is rigidly attached to the magnetron. 

To prevent microwave leakage, tighten the mounting screws properly, making sure there is no gap between the waveguide and the magnetron.

REMOVING THE TURNTABLE MOTOR
1) Remove the glass tray.
2) Remove the pulley shaft VERY CAREFULLY
3) Lay the unit down on its back.
4) Remove the turntable motor cover.  The turntable base cover is easily removed by pinching the six parts with a wire cutting.
5) Disconnect the leadwire from the turntable motor terminals.
6) Remove the screw securing the turntable motor to the oven cavity ASS’Y
7) After rep the motor, rotate the removed turntable motor cover.
8) Fit the turntable motor cover’s projecting part to the base plate slit.

NOTE:
1. Remove the wire lead from the turntable motor VERY CAREFULLY.

2. Be sure to grasp the connector, not the wires, when removing.

INTERLOCK SYSTEM

1) INTERLOCK MECHANISM

The door lock mechanism is a device which has been specially designed to eliminate completely microwave activity when the door is opened during cooking and thus to prevent the danger resulting from the microwave leakage.

2) MOUNTING OF THE PRIMARY/MONITOR/ SECONDARY SWITCHES TO THE LATCH BOARD.

3) INSTALLATION AND ADJUSTMENT OF THE LATCH BOARD TO THE OVEN ASSEMBLY

• Mount the latch board to the oven assembly.

• Adjust the latch board in the arrow direction so that oven door will not have any play in it when the door is closed.

• Tighten the mounting screw.

• Check for play in the door by pushing the door release button. Door movement should be less than 0.5 mm. (1/64 inch).  Don't push the door release button while making adjustment. Make sure that the latch moves smoothly after adjustment are completed and that the screws are tight. Make sure the primary, monitor, and secondary switches operate properly.

PRIMARY INTERLOCK SWITCH TEST

When the door release button is depressed slowly with the door closed, an audible click should be heard at the same time or successively at intervals. When the button is released slowly, the latches should activate the switches with an audible click.

If the latches do not activate the switches when the door is closed, the switches should be a adjusted in accordance with the adjustment procedure. Disconnect the wire lead from the

primary switch. Connect the ohmmeter leads to the common (COM) and normally open (NO) terminal of the switch. The meter should indicate open circuits in the door open condition.

When the door is closed, the meter should indicate a closed circuit.  When the primary switch operation is abnormal, make the necessary adjustment or replace the switch only with the same type of switch.

SECONDARY INTERLOCK SWITCH TEST

Disconnect the wire lead from the secondary switch.

Connect the ohmmeter leads to the common (COM) and normally open (NO) terminals of the switch. The meter should indicate a open circuit in the door open condition. When the door is closed, meter should indicate an closed circuit. When the secondary switch operation is abnormal, make the necessary adjustment or replace the switch only with the same type of switch.

MONITOR SWITCH TEST

Disconnect the wire lead from the monitor switch.  Connect the ohmmeter leads to the common (COM) and normally closed (NC) terminals of the switch. The meter should indicate closed circuit in the door open condition. When the door is closed, meter should indicate an open circuit. When the monitor switch operation is abnormal, replace with the same type of switch.

NOTE: After repairing the door or the interlock system, it is necessary to do this continuity test before operating the oven.

Circuit diagram [Click on the pictures to magnify]

Troubleshooting

The following visual conditions indicate a probable defective control circuit.

1) Incomplete segments.
> Segment missing.
> Partial segment missing.
> Digit flickering (NOTE: Slight flickering is normal.)
2. Colon does not turn on or blink.
3. A distinct change in the brightness of one or more numbers in display.
4. One or more digits in the display are not lighting.
5. Display indicates a number different from one touched, for example, key in 5 and 3 appears in the display.
6. Specific numbers (for example 7 or 9) will not display when key pad is touched.
7. Display does not count down with time blinking or up with clock operation.
8. Display obviously jumps in time while counting down.
9. Display counts down too fast while cooking.
10. Each indicator light does not turn on after setting cooking cycle.
11. Display time of day does not reappear when cooking is finished.
12. Beep sound is not heard when correct key is touched.

Oven does not operate at all ; Display window does not display any figures and no input is accepted.

NOTE: All these switches must be replaced at the same time.

Display shows all figures set, but oven does not start cooking while desired program times are set and START pad is touched.

No microwave oscillation even though oven lamp and fan motor run (Display operates properly)

Oven does not cook properly when programmed for the set power level (Operates properly on HIGH)