R-757M (serv.man6). Operation sequence and function of important components - Sharp Home Appliance Service Manual (repair manual). Page 2

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R-757M - 7
DOOR OPEN MECHANISM
The door can be opened by pulling the door handle. When
the door handle is pulled, the latch head is moved upward,
and released from the latch hook, now the door can be
opened.
Figure D-1. Door Open Mechanism
Basis cooking time
Reduced power output
Cooking mode
 (minutes)
(%)
Microwave (100%)
20
70
Grill
30
50
DUAL (Micro
10%-70%) + Grill
30
50 (Grill)
NOTE:
1. If the multiple sequence cooking is carried out in the
same mode, the basis cooking time is calculated from
the first.
2. Even if the cooking is stopped by the STOP/CLEAR
key or opening the door, the basis cooking time is
calculated from the first.
3. If the same cooking mode is repeated within 1 minute
and 15 seconds, the basis cooking time is calculated
from the first.
4. If the same manu of automatic cooking is repeated
within 1 minute and 15 seconds, the power output of
the microwave or the grill will be reduced to 70% after
20 minutes when the oven is started at first.
DUAL COOKING CONDITION
In this condition the food is cooked by both microwave
energy and grill heating element energy simultaneously.
Enter the desired cooking time by pressing TIME keys.
And choose the dual grill mode by pressing DUAL GRILL
key. And choose the microwave power level by pressing
DUAL GRILL or MICROWAVE POWER LEVEL key. When
the  START key is pressed, the following operations occur:
Figure O-4 on page 26
1. The relays RY1,RY2 and RY3 are energized.
2. The numbers on the digital read-out start the count
down to zero.
3. Then following components are energized.
High voltage transformer
Grill heating element
Magnetron
Turntable motor
H.V. capacitor
Fan motor
H.V. rectifier
Oven lamp
4. Now, the food is cooked by microwave and grill heating
element energy simultaneously.
5. Upon completion of the selected cooking time, audible
signal sounds, and contacts of relays are opened, then
the activated cpmponents as items 3 are de-energized.
6. When cooking in dual mode the microwave power is
limited to 70% (via the I.C.).
EXPRESS DEFROST/ EXPRESS COOK/ MEAL IN
ONE/AUTO CLOCK PROGRAMME
The cooking modes and cooking time are automatically
computed and selected based on the programmes.
ON/OFF TIME RATIO(DUAL MODE)
In DUAL cooking, the magnetron operates within a 48
second time base. The following table is the ON / OFF time
ratio at each power output of the magnetron.
POWER OUTPUT
ON TIME
OFF TIME
100%
48 sec.
0 sec.
70%
36 sec.
12 sec.
50%
26 sec.
22 sec.
30%
16 sec.
32 sec.
10%
8 sec.
40 sec.
POWER OUTPUT REDUCTION
After the same cooking mode is carried out for more than
the basis cooking time, the power output is automatically
reduced by turning the control relays on and off intermit-
tently, as shown in the table below. This is to protect the
oven door against temperature rising.
FUNCTION OF IMPORTANT COMPONENTS
MONITORED LATCH SWITCH AND STOP SWITCH
1. When the oven door is closed, the contacts (COM-NO)
must be closed.
2. When the oven door is opened, the contacts (COM-
NO) must be opened.
MONITOR SWITCH
1. When the oven door is closed, the contacts (COM-NC)
must be opened and contacts (COM-NO) must be
closed.
2. When the oven door is opened, the contacts (COM-
NC) must closed and contacts (COM-NO) must  open.
3. If the oven door is opened and the contacts  (COM-NO)
of the monitored latch switch fail to open, the fuse (F8A)
blows simultaneously with closing the contacts (COM-
NC) of the monitor switch.
Latch Hooks
Stop Switch
Monitor 
Switch
Monitored
Latch 
Switch
OPERATION SEQUENCE
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