Operation, Description of Operating Sequence

OPERATION

DESCRIPTION OF OPERATING SEQUENCE

The following is a description of component functions during oven operation.

(RD71101 U)

OFF CONDITION

Closing the door activates both door interlock

switches: upper latch switch, lower latch switch and

stop switch. (In this condition, the monitor switch contacts are opened.)

When oven is plugged in, 240 volts A.C. is supplied to the relay unit. (Figure O-l).

1. The display will show flashing “88:88”. ’

To set any program or set the clock;- you must first touch the STOP/CLEAR pad. The display will clear, and I:00 will appear and count up every minute.

Note: When the door is opened, the oven lamp comes

2.A si;al is input to the control unit, energizing the coil of shut-off relay (RY6).

RY6 contacts close, completing a circuit to the damper motor.

The damper motor now operates moving the damper to the open position, thereby closing the contacts of the damper switch inputs a signal to the control unit.

The coil of relay RY6 is de-energized, opening its

contacts, thereby turning off the damper motor.

(RD71207U)

COOKING CONDITION

HIGH COOKING

Program desired cooking time and Variable Cooking Control by touching the NUMBER pads and the HIGH pad of the Variable Cooking Control. When the START pad is touched, the following operations occur:

1.The contacts of relays are closed and components connected to the relays are turned on as follows. (For details, refer to Figure O-2)


RELAY	CONNECTED COMPONENTS
RY-1	power	transformer
RY-2	oven	lamp/turntable motor
RY-3	convection		motor
RY-4	convection		heater
RY-5	fan motor
RY-6	damper motor

2.240 volts A.C. is supplied to the primary winding of the power transformer and is converted to about 3.3 volts A.C. output on the filament winding, and approximately 2043 volts A.C. on the high voltage winding.

3.The filament winding voltage heats the magnetron filament and the H.V. winding voltage is sent to a voltage doubler circuit.

4.The microwave energy produced by the magnetron is channeled through the waveguide into the cavity feed-box, and then into the cavity where the food is placed to be cooked.

5.Upon completion of the cooking time, the power transformer, oven lamp, etc. are turned off, and the

generation of microwave energy is stopped. The oven will revert to the OFF condition.

6.When the door is opened during a cook cycle, monitor switch, upper latch switch, lower latch switch and stop switch. are activated with the fol- lowing results. The circuits to the turntable motor, the cooling fan motor, and the high voltage com- ponents are deenergized, the oven lamp remains on, and the digital readout displays the time still re- maining in the cook cycle when the door was

opened.

7 . The monitor switch is electrically monitoring the operation of the upper latch switch and is mechan- ically associated with the door so that it will func- tion in the following sequence.

(1)When the door opens from a closed position, the upper latch switch and lower latch switch open their contacts, and then the monitor switch contacts close.

(2)When the door is closed from the open posi- tion, the monitor switch contacts first open,

and then the contacts of the upper latch switch and lower latch switch close.

If the common and normal open contacts of upper latch switch fail with their contacts closed when the door is opened, the closing of the monitor switch contacts will form a short circuit through the fuse and upper latch switch, causing the monitor fuse to blow.

MED HIGH, MED, MED LOW (DEFROST), LOW, HOLD COOKING

When Variable Cooking Power is programed, the 240 volts A.C. is supplied to the power transformer

intermittently through the contacts of relay( RY-2) which is operated by the control unit within a 32 sec- ond time base. Microwave power operation is as fol- lows:

VARI-MODE			ON TIME		OFF TIME
HIGH			32	sec.	0	sec.
(100%	power)
MED HIGH			24	sec.	8	sec.
(approx.	70%	power)
MED			18	sec.	14	sec.
(approx.	50%	power)
MED LOW (DEFROST)			12	sec.	20	sec.
(approx.	30%	power)
LOW			6	sec.	26	sec.
(approx.	10%	power)
HOLD			0	sec.	32	sec.

(0% power)

Note: The ON/OFF time ratio does not correspond with the percentage of microwave power, be- cause approx. 2 seconds are needed for heating of the magnetron filament.

(RD71401 U)