Sharp R-9370 User manual

R-9370
SHARP SERVICE MANUAL
S7607R9370J//
MICROWAVE OVEN
MODEL R-9370
In the interests of user-safety the set should be restored to its
original condition and only #parts identical to those specified be
used.
This isa supplemental Service Manual for R-9370.
This model is quite similar to Base Model R-9360.
Model R-9370 has Reheat Sensor function in addition, compared to its base model R-9360.
Use this supplemental manual together with the BaseService Manual.
Refer to the Base Service Manual for complete operation, service information, etc.
cc TABLE OF CONTENTS Y
Page
FOREWORD ...................................................................... 1
CAUTION, MICROWAVE RADIATION ................................................... 1
THUMB INDEX ................................................................... 1
PRODUCT DESCRIPTION ............................................................ 2
OPERATING INSTRUCTIONS ......................................................... 3
SERVICING ....................................................................... 6
TOUCH CONTROL PANEL ASSEMBLY. ................................................. 8
MICROWAVE MEASUREMENT ....................................................... 21
SCHEMATIC DIAGRAM ............................................................ 22
PICTORIAL DIAGRAM ............................................................. 22
CONTROL PANEL CIRCUIT ......................................................... 23
PRINTED WIRING BOARD .......................................................... 24
PARTS LIST .................................................................... 25
PACKING AND ACCESSORIES.. ..................................................... 34
SHARP CORPORATION

R-9370
SERVICE MANUAL
SHARP
MICROWAVE OVEN
R-9370
FOREWORD
This Manual has been prepared to provide Sharp Service
Personnel with complete Operation and Service information
for the Sharp Microwave Oven.
This model isquite similar to Base Model R-9360.
(Ref. No. SO506R936OJ//).
It is recommended that service personnel carefully study the
entire text of two Manuals (Base manual and this manual),
so they will be qualified to render satisfactory customer
service.
CAUTION
MICROWAVE RADIATION
Personnel should not be exposed to the microwave energy
which may radiate from the magnetron or other microwave
generating devices if it is improperly used or connected,
All input and output microwave connections, waveguides,
flanges, and gaskets must be secured.
Never operate the ‘devicewithout a microwave energy absorbing
load attached.
Never look into an open waveguide or antenna while the
device is energized.
SHARP CORPORATION
OSAKA, JAPAN

R-9370 PRODUCT DESCRIPTION
EXPLANATION OF MICROWAVE COOKING
‘Xhe Sharp Microwave Oven usesmicrowave energy to produce
heat in the food to be cooked. Unlike conventional ovens
microwave energy will cook foods without applying external
heat.
Microwaves, which are short electromagnetic waves of RF
(radio frequency) energy, passthrough materials such as glass,
paper, china and most plastics. Materials such as metal and
aluminum foil tend to reflect microwaves and may be used
only as recommended in the cooking instructions.
Materials with a high moisture content, like most foods, will
absorb microwave energy. As the microwave energy at a fre-
quency of 2450 Megahertz enters the food, the molecules align
themselves with the energy. Because the microwaves are
changing polarity every half cycle, the food molecules are
changing direction every half cycle or oscillating back and
forth 4,900,000,000 times per second. This high speed oscil-
lation causes friction between the molecules, thereby convert-
ing the microwave energy to heat.
SPECIFICATIONS
ITEMS
Power requirements
DESCRIPTIONS
240v
50Hz
Single phase, 3 wire earthed
Power consumption
Microwave output power
Case dimensions
Width
Height
Depth
Cooking cavity dimensions
Width
Height
Depth
Turntable diameter
Control complement
1.4kW
700W (2 litre water load)
622mm
382mm
476mm
406mm
248mm
422mm
395mm
Clock (l:OO- 12:59)
Minute Timer (0- 99 minutes 99 seconds)
Variable Cooking Mode Selector
Repetition Rate:
HIGH .........................Full power throughout the cooking time
MED HIGH .................24 sec. ON, 8 sec. OFF, approx. 70% of full power
MED .......................... 18 sec. ON, 14 sec. OFF, approx. 50% of full power
MED LOW
DEFROST ...................12 sec. ON, 20 sec. OFF, approx. 30% of full power
LOW ..........................6 sec. ON, 26 sec. OFF, approx. 10% of full power
Auto Start Cooking
Instant Cooking
Compu. Defrost Cooking
Reheat Sensor Cooking
Weight Approx. 27kg
2

R-9370
OPERATING INSTRUCTIONS
OPERATION OF AUTO-TOUCH” CONTROL
PANEL
Your new Auto-Touch microwave oven uses a microprocessor, the electronic brain that provides the
wide variety of cooking programmes which could not be achieved by conventional control methods. The
operation of the oven is controlled by touching the appropriate pads arranged on the surface of the con-
trol panel. The lighted digital readout will display the cooking time, Sensor Cook, or Compu Defrost set- I
ting or time:of day or minute timer. Indicators show the variable cooking setting and cooking function
you have programmed.
An entry signal tone should be heard each time you touch the control panel to make a correct entry.
If you do not hear this sound,
1) You have not used enough pressure in touching the pad.
2) You have made more entries than the control panel will accept.
3) You have made an incorrect entry. I
In addition to the entry signal tone, an audible signal will sound for approximately 2 seconds at the end
of the cooking cycle.
* Make sure the oven is plugged into a power point. When the oven is plugged in, the display show
[88:581, flashing on and off each second. Touch the STOP/CLEAR pad: [“-?F] will appear.
* You cannot programme the oven if the door is not closed firmly.
* During cooking, the programme cannot be changed until the STOP/CLEAR pad is touched twice.
All functions are locked in to prevent accidental changes.
If food does not seem to be heating properly, check the indicator immediately below the lighted digital
display. Be sure the Variable Cooking Control is on the proper setting.
* If the electrical power supply to your microwave oven should be interrupted, the display will intermit-
tently show 185:88] after the power is reinstated. If this occurs during cooking, the programme will
be erased. The time of day will be also erased. Simply reset the clock for the correct time of day.
Auto-TouchTMControl Panel
I 7 INDICATORS
LIGHTED DIGITAL DISPLAY
CMP”MfOLowMI0“IL” Shows readout of cooking time, cooking instruction or time of day.
7
3
3
9 r
NUMBER PADS
Touch to enter cooking times, clock time or weight of food.
REHEAT SENSOR PAb
Touch to reheat food.
COMPU DEFROST PAD
Touch to select Compu Defrost settings.
VARIABLE COOKING CONTROL PADS
Touch to select microwave power-setting. If not touched, HIGH
is automatically selected.
STOP/CLEAR PAD
Touch to erase during programming.
Touch once to stop operation of oven during cooking; touch twice
to cancel cooking program.
AUTO START/CLOCK PAD
Touch to set clock or auto start time.
START PAD
Touch to start oven.
INSTANT COOK PAD
Touch to cook for 1 minute at HIGH or increase by 1 minute mul-
tiples during variable cooking.
TIMER/HOLD PAD
Touch to set minute timer or HOLD function.
3

R-9370
Reheat Sensor
HOW ONE TOUCH REHEAT SENSOR WORKS
Sharp’s Electronic Sensory Processor is a semi-conductor device that detects the vapor (humidity) emit-
ted from food as it heats. The Sensor adjusts cooking times and variable power for various foods and
quantities. It takes the guesswork out of microwave heating.
HERE’S AN EXAMPLE OF HOW IT WORKS: &cq *‘Cg
,O%&. 0%
f [ SENSOR j kc
1. Broccoli at room temperature. 2. Heat Broccoli. Vapor is emitted 3. Sensor detects vapor and cal-
Vapor is emitted very slowly. rapidly. culates cooking time and vari-
Before You Use REHEAT SENSOR able power.
1. The oven should not be operated on Sensor Reheat immediately after plugging in the unit. Wait 5
minutes before using the Sensor Reheat.
2. The Reheat Sensor is designed to work best for reheating one to two servings of precooked foods.
The Reheat Sensor may not work perfectly with all menus. Please refer to reheat chart for available
menus.
3. Be sure the exterior of the cooking container and the interior of the oven are dry. Wipe off any moisture
with a dry cloth or paper towel.
4. Room temperature should not exceed 35OC.
5. Dense casseroles are difficult to heat with the Reheat Sensor and may be too cool. Stirring the cas-
serole after heating will help to equalize temperatures.
6. If the Reheat Sensor has not detected the vapor of the food after 15 minutes, [E,c,c3,c] and IRE-
-1 will appear in the display and the oven will shut off.
Selecting Foods
1. Reheat Sensor works with foods at normal storage temperature. For example, chicken pieces would
be at refrigerator temperature and canned soup at room temperature.
2. A minimum quantity of a half cup should be heated when using the Reheat Sensor. Smaller quantites
should be heated by time and variable power.
3. Should foods be cooler than desired, simpiy heat an additional minute or two using Instant Cook pad.
4. If a particular food is hotter than desired, consult your cookbook or cooking guide and choose time
and variable power the next time the food is heated.
5. The arrangement of foods will affect heating results. Place the thickest parts of foods to the outside
of the dish, where they will receive more microwave energy.
6. When possible, stir foods before eating.
Covering Foods
Foods should be covered with plastic wrap or casserole lid when using the Reheat Sensor. Other cover-
ings may cause foods to overheat.
1. Casserole lid.
2. Plastic wraps.
Use plastic wraps recommended for microwave cooking.
Cover dish loosely; fold excess wrap over side of dish.
Do not create an air tight seal, follow procedure in chart.
Be careful when removing any covering to allow steam to escape away from you.
1. Casserole lid 2. Plastic wrap

R-9370
I I
/ To Use Reheat Sensor 1
To use the Reheat Sensor, open oven door, place food in oven, close door and touch the Reheat Sensor
pad. The REHEAT SENSOR pad must be touched within one minute after closing oven door or touching
the STOP/CLEAR pad.
+ Suppose you want to reheat vegetables.
-Step Procedure Pad Order I
1. Touch REHEAT SENSOR pad. I REHEAT I
I I --
SENSOR 1
Display
SENSOR
ICOOK
and
They will be displayed con-
tinuously.
The oven will start operating. When the food is hot as detected by the reheat sensor, all indicators will
go out and an audible signal will sound. The time of day will reappear on the display.
NOTE: Avoid opening the oven door or touching STOP/CLEAR pad when ml m:--(EISTl is displayed.
If this occurs, -1 and IRE-1 (1 will appear and sensor heating will be interrupt-
ed. To continue heating, touch STOP/CLEAR pad. -1 and (-1 I] indicator will
go out. Select heating time and variable power level. Heating with the Reheat Sensor at this point
may result in overheating.
Reheat Chart
FOOD QUANTITY
soup
Dinner Plate
Casserole
Meat Sauce
Canned Food
Steak
Chops
Sliced Roast Beef
Hamburger Patties
Chicken Pieces
Fried Rice
Hot Dog
Sweet Fruit Pie
1-4 cups
1 serving
200-1ooog
200-800g
200-IOOOg
l-4
l-6
200-5oog
2-6
2-4 pieces
200-1ooog
l-2
1-4 pieces
UTENSIL
Casserole
Plate
I Casserole
Mixing Bowl
1
1 Plate
Mixing Bowl
-
Plate’
I COVER
Lid or Plastic Wrap
Plastic Wrap
Lid or Plastic Wrap
Plastic Wrap
Plastic Wrap
Plastic Wrap
Paper Towel
No
5

R-9370 SERVICING
TROUBLESHOOTING GUIDE
Note: For other Test Procedures, please refer to Service Manual for Base Model R-9360.
PROBLEM POSSIBLE CAUSE TEST PROCEDURE OR
CORRECTION
SENSOR COOKING
Oven is in the sensor cooking con-
dition but RH sensor does not end
stage 1. of cooking cycle, cooking
cycle or does not step cooking
cycle.
RH sensor open and/or short. Procedure K.
Defective control unit. Procedure K.
Open or loose wire connection to the above Check and repair wiring.’
-. components.
TEST PROCEDURES (CONT’D)
PROCEDURE
LETTER COMPONENT TEST
J KEY UNIT TEST
If the Indicator does not respond to touching a key Pad use the following matrix and place a jumper wire
between the proper pin connections with the G (1a-pin) cable disconnected from the control unit.
If the indicator responds and oven goes into operation, the key unit is faulty.
If there is no response, replace the control unit.
.
6

R-9370
TEST PROCEDURES (CONT’D)
PROCEDURE
LETTER COMPONENT TEST
K REHEAT SENSOR TEST
Water Load Cooking Test
Check as follows:
(1) Fill 36 milliliters (1 oz) of tap water initially at 2O+l”C (68°F) in a 100 milliliter measuring cup
(2) Place the container on the edge of turntable tray in the oven cavity.
(3) Close the door, and touch “REHEAT SENSOR” pad.
(4) The oven is in the sensor cooking condition.
(5) Sensor cooking time should be 66+35 seconds.
Checking the Control Unit with Use of Dummy Resistor.
(1) Take the procedures according to the instructions in “Servicing of Touch Control Panel”.
Besides it is needed to connect the parts asshown in Fig. A to the connector (C) to enable checking
of the REHEAT SENSOR.
(2) Check the sensor cook operation proceed as follows:
(2-l) Touch REHEAT SENSOR pad.
(2-2) The control panel is in the sensor cooking operation.
(2-3) After approximately 40 seconds, push plunger of MICRO switch.
This condition is same asjudgement by REHEAT SENSOR.
(2-4) After approximately 3 seconds, cooking operation turns off, an audible signal will sound, and the
display will then revert to the time of day.
If the above is not case, the control unit is probably defective.
If the above is proper, the REHEAT SENSOR is probably defective.
MICRO
SWITCH
Figure A. Sensor Dummy Resistor Circuit

R-9370 TOUCH CONTROL PANEL ASSEMBLY
OUTLINE OF TOUCH CONTROL
The touch control section consists of the following units as
shown in the block diagram.
(1) Key unit
(2) Control unit
Exchange of signals between each unit is indicated by the ar-
rows in the block diagram. The principal functions of these
units and the signalscommunicated among them are explained
below.
l-l. Key Unit
The key unit is composed of a matrix, signals generated
in the LSI are sent to the key unit through P62, P63,
P70 - P73. When a key pad is touched, a signal is com-
pleted through the key unit and passed back to the LSI
through PlO - P13 to perform the function that was
requested.
l-2. Control Unit
Control unit consists of LSI, Power source circuit, Syn-
chronizing signal circuit, ACL circuit, Buzzer circuit,
Reheat sensor circuit and Indicator circuit.
1) Power Source Circuit
This circuit generates voltage necessary in the control
and indicator circuit, from the AC line voltage. In ad-
dition, the synchronizing signal is available in order to
compose a basic standard time in the clock circuit.
2) Synchronizing Signal Circuit
The power source Synchronizing signal is available in
order to compose a basic standard time in the clock
circuit.
It accompanies a very small error because it works on
the commercial frequency.
3) LSI (IX2412YA)
This LSI controls the reheat sensor signal, key touch
and relay control signal for oven function, and control
of the indicator circuit.
4) ACL
A circuit to generate a signal which resets the LSI to
the initial state when power is supplied.
5) Stop switch
A switch to “tell” the LSI if the door is open or closed.
6) Buzzer
The buzzer is responsive to signals from the LSI to
emit noticing sounds (key touch sound and completion
sound).
7) Relay Circuit
To drive the magnetron, fan motor, turntable motor
and light oven lamp.
8) Reheat Sensor Circuit
This circuit detects moisture of a food which is under
cooking, to allow its automatic cooking.
9) Indicator Circuit
This circuit consists of 6-digits, 13 segments display,
five cooking mode indicators.

R-9370
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R-9370
3. DESCRIPTION OF LSI
LSI (ICl: lX2412YA)
The I/O signals of the LSI are detailed in the following tables.
P30
P31
P32
P33
ACL
CL1
ci2
P40
TEST
P41
P42
P43
P50
P51
P52
P53
P60
P61
P62
P63
P70
P71
P72
P73 1 1
24
KT 1 25 1
58
l-i
57
IX2412YA
GND
P23
P22
P21
P20
PA0
PA1
VR
Vdisp
PA2
PA3
PA4
PA5
PA6
PA7
PA8
PA9
AGND
P13
P12
Pll
PlO
PO3
PO2
PO1
PO0
P93
P92
P91
P90
P83
P82
Figure T-2. Relationship between pin Nos. and Signals (LSI: IX2412YA)
10

R-9370
Pin No. Signal I/O Description
1 P30 OUT Segment data signals
The relation between signals and segments are as follows:
Signal Segment
P20 . . , . . . . . . . . . . . d
P21 . . * . . . . , * . . . * . c
P22 , . . . , . . . . . . . . . b
P23 . . . . . . . . . . . . . . a
P30 . . . . . . . . . . . . . . e
p31 . . . . . .*, . , . . *, f
P32 . . . . . . . . . . . . . . g 1.68 msec.
P33 , . . . . , . . . . . . . . h --- GND
~40 . . . . , . . . . . . . . . i a ....-... DEFROST
~41 . . . . . . . . . . . . . . j b. -. - - - a. SENSOR Segment
I-
Signal
P42 . . . . . . . . . . . . . . k -27V
P31 OUT
P32 OUT
P33 OUT
ACL IN Auto-clear terminal
Signal is input to reset the LSI to the initial state when power is supplied. Temporarily set
to “L” level the moment power is supplied, at this time the LSI is reset. Thereafter set at
“H” level.
CL1 IN internal clock oscillation frequency setting input.
The internal clock frequency is set by inserting the ceramic filter oscillation circuit with
respect to CL2 terminal.
CL2 OUT Internal clock oscillation frequency control output.
Output to control oscillation input of CLl.
8 P41 OUT Segment data signal.
Signal similar to P30.
9 TEST IN Not used. Connected to VDD (--12V).
10 P40 OUT Segment data signal.
Signal similar to P30.
11 P42 OUT
OUT Signal for lighting of Power level and COMPU indicators. 12
13
P43
P50
Signal similar to P30.
OUT Signal for lighting of COOK, AUTO and kg indicators.
Signal similar to P30.
14 P51 IN Terminal not used.
P52
151 IN
IN
IN
IN
OUT
Not used. Terminal for manufacture test.
Terminal not used.
Key strobe signal.
Signal applied to touch-key section.
A pulse signal is input to PlO - P13 terminal while one of G-l line keys on key matrix is
touched.
OUT Key strobe signal.
Signal applied to touch-key section.
4 pulse signal is input to PlO - P13 terminal while one of G-2 line keys on key matrix is
touched.
16 P53
P60
P61
P62
17
18
19
T
11

R-9370
Pin No. Signal I/O Description
21 P70 OUT Key strobe signal.
Signal applied to touch-key section.
A pulse signal is input to PlO - P13 terminal while one of G-3 line keys on key matrix is
touched.
22 P71 OUT Key strobe signal.
Signal applied to touch-key section.
A pulse signal is input to PlO - P13 terminal while one of G-4 line keys on key matrix is
touched.
23 P72
24 P73
OUT
OUT
Key strobe signal.
Signal applied to touch-key section.
A pulse signal is input to PlO - P13 terminal while one of G-5 line keys on key matrix is
touched.
Key strobe signal.
Signal applied to touch-key section.
A pulse signal is input to PI0 - P13 terminal while one of G-6 line keys on key matrix is
touched.
25 KT
26 KI
27 so
IN Terminal not used.
IN
OUT Signal to sound buzzer.
A: Key touch sound. 0.12 sec.
6: Completion sound.
A. -//-
B
28 NC
29 VDD
30 P80
31 P81
32 GND
33 P82
34 P83
35 P90
36 P91
37 P92
38 P93
NC
IN
OUT
IN
IN
IN
OUT
OUT
OUT
OUT
OUT
Not used.
Power source voltage: -12V.
VDD Voltage of power source circuit input.
Terminal not used.
Connected to GND.
Terminal not used.
Used for initial balancing of the Reheat Sensor circuit.
12

R-9370
Pin No. Signal I/O Description \
39 PO0 IN RH sensor input.
This input is an analog input terminal from the RH sensor circuit, and connected to the A/D
converter built into the LSI.
40 PO1 IN Terminal to change the functions according to the Model.
By using the A/D converter contained in the LSI (lX2412YA), DC voltage in accordance
with the Model in operation is applied to set up its function.
41 PO2 IN
42 PO3 IN
Not used. Connected to GND.
Terminal to change the functions according to the Model.
By using the A/D converter contained in the LSI, DC voltage in accordance with the Model
in operation is applied to set up its function.
43 PlO IN Signal coming from touch-key.
When either one of G-l 1 line keys on keys on key matrix is touched, a corresponding signal
out of P70 - P73, P63 and P62 will be input into PlO.
When no key is touched, the signal is held at “L” level.
44 Pll IN
45 P12 IN
Signal similar to PIO.
When either one of G-10 line keys on key matrix is touched, a corresponding signal will be
input Pll. -
Signal similar to PIO.
When either one of G-9 line keys on key matrix is touched, a corresponding signal will be
input P12.
46 P13 IN Signal similar to PlO.
When either one of G-8 line keys on key matrix is touched, a corresponding signal will be
input P13.
47
48
49
50
51
52
53
AGND IN Connected to GND.
PA9 OUT Digit selection signal.
~ The relation between digit signal and digit are as follows:
PA8 OUT Digit Signal Digit
PA7 OUT PA4 . . . . . . . . . . . 1st
PA5 . . . . . . . . . . . 2nd 1.32 msec.
PA6 OUT PA6 . . . . . . . . . . . 3rd
PA7 . . . . . . . . . . . 4th PA4
PA5 OUT PA8 . . . . . . . . . . . 5th
PA9 . . . . . . . . . . . 6th
T--------- ;;;”
PA4 OUT Normally, one pulse is output in every
I3period, and input to the grid of the PA5 n
Fluorescent Display.
PA6 1 .
PA7 1
PA8 1
PA9a ;:p,
1.32 msec.
13

R-9370
Pin No. Signal I/O Description
54 PA3 OUT *Oven lamp cooling fan motor and turn table motor driving signal (Square waveform:
50Hz).
To turn on and off the shut-off relay (RYl):
The Square waveform voltage (50Hz) is delivered to the RYl driving circuit and RY2
control circuit.
20 msec.
t- -
-v-m- GND
-19v
During cooking or when door is opened.
55 PA2 OUT Magnetron high-voltage circuit driving signal.
To turn on and off the cook relay (RY2).
In HIGH operation, the signals holds “H” level during microwave cooking and “L” level
while not cooking. In other cooking modes (HIGH, M-HIGH, MED, M.LOW, LOW) the
signal turns to “H” level and “L” level in repetition according to the power level.
HIGH J’
MED HIGH p.n;;;.{
MED ~~-oF~~c f
MED LOVVj-+f
LOW
32sec. cl
HOLD --- L
56 Vdisp IN Anode (segment) of Fluorescent Display light-up voltage: -27V.
Vp voltage of power source circuit input.
57 VR IN Reference voltage input terminal.
A reference voltage applied to the A/D converter in the LSI.
The reference voltage is generally maintained at -6.15V.
58 PA1 IN Signal synchronized with commercial source frequency.
This is the basic timing for time processing of LSI (ICl: lX2412YA).
‘r;L IT-r:
I
I
I I
I 20 msec. I
‘1
14

Pin No. Signal I/O Description
59 ’ PA0 IN input signal which communicates the door open/close information to LSI.
Door closed: “H” level signal (OV)
Door opened: “L” level signal (-12V)
60 P20 OUT Segment data signals.
l3’ I P21 OUT - Signal similar to P30.
62 P22 OUT
63 P23 OUT
64 GND IN Connected to GND.
POWER SOURCE CIRCUIT
A power of AC 240V is applied to the primary winding of smoothed by the electrolytic capacitor (C2) to become DC
transformer (Tl). voltage VC. Then the voltage VC is delivered to the constant
The output voltage of the secondary winding of transformer voltage circuit.
(Tl) is then full-wave rectified by the diode bridge (Dl) and VDD (-l2V) is a voltage to be applied to the LSI.
Tl Dl
POWER
SUPPLY
240V 50Hz
To Relay Contact
+ c70
To Relay Circuit f
Figure T-3. Power Source Circuit
15

R-9370 SYNCHRONIZING SIGNAL CIRCUIT
At the secondary side of the power source circuit there is to PA1 terminal of LSI. This voltage is referred to as a power
caused AC half-wave rectified voltage and it is applied via R7 sync. signal.
R7 58
> 11. - - c PA1
LS I
J--\ i'"'
I I
I 20.0 msec. I
I-- -l
Figure T-4. 13Circuit and Waveform
ACL CIRCUIT
By switching on power, charge current (il) is fed to C20
through R20 and generates throshold voltage (Vz).
If Vz exceeds the zener voltage of ZD20, ZD20 is turned on
and the current 2 flows. Thus, placing voltage on to the base
of transistor 020 and turning it on.
A reset signals is obtained from the collector.
C21: Noise filter capacitor.
GND, a *
v w v
I 1 Q20
--
j/z;+ il r ---1
I
I =c20 I - c21
t * 2020 ; u I
I I T
voD> fz- L---p-
(-12V)
RESET
GND
RESET
J
Figure T-5. ACL C
ircuit
16

BUZZER CIRCUIT
The square waveform developed from T terminal of LSl is
applied to the base of Q30 to turn on and off 030, and square
waveform voltage (2.5 kHz) is applied to SPI to generate
buzzer sound.
SPl
I
I I (From LSL)
r T 1
I <So Pin NO. 27
Figure T-6. Buzzer Circuit
RELAY CIRCUIT
While the unit is in cook, “H” level signal is produced at succession so that a current II is caused to turn on the control
PA2 terminal of LSI and also a pulse signal at PA3 terminal of relay (RYI).
LSI. The pulse signal form PA3 terminal is applied to the rec- The “H” level signal from D6 terminal is applied to 080 which
tifier circuit made up of Diodes DIOO and DlOl inside the
hybrid IC (IC3) where it is made into DC signal to charge
is connected in series with QlOl, and current i2 made only
when both Q80 and QlOl are turned on at the same time
ClOO. With Cl00 charged up, QIOO and 0101 turn on in allowing the cook relay (RY2) to turn on.
R-9370
To Power !
Source Circait
t
DTC114EA 2
080
r----7
4 I “H” 55 I
PA2 vJ,
I
II /I I nnnnnn
-I I
DlOO
, I
R104
+c(- ,, 1
H
R103 I3101 Cl01 ‘“” 15
R105
I RlOl
--I-
1 J
IC3 : Hybrid IC 4
vz
Figure T-7. Relay Circuit
17

R-9370
REHEAT SENSOR CIRCUIT
1. Operational Principle of Reheat Sensor
As shown in Fig. T-8,2 pieces of temperature sensitive resis-
and RH, are used in the detector of the reheat sensor. These
temperature sensitive resistors are cased for protection.
Fig. T-9 shows the basic circuit. The temperature sensitive
resistor RH, is receiving approx. 52mA of current at all times,
keeps itself heated to approx. 460°F (240°C).
A minute current is applied to the temperature sensitive resis-
tor RN to measure the ambient temperature.
VOUT (output voltage) in Fig. T-9 can be expressed as
follows.
RH
VOUT = - RN lo l Rf
Where, lo is a constant current and Rf is a fixed
resistance.
Therefore, VOUT will be the voltage in proportion to the
resistance ratio between RH and RN.
The temperature sensitive resistors RH and RN have a linear
and positive characteristic against the temperature. Therefore,
when the temperat;; is the only varying force with humidity
being constant, R
value at a constant evel.
r becomes constant, keeping VOUT
When vapors are produced from the food, the RH resistor side
is cooled down reducing the temperature, making the
resistance lower. Therefore, a VOUT voltage is generated in
proportion to the variation of vapor volume.
Internal Structure al Fft-i Sensor
Figure T-8.
Operational
amplifier
Rf
output
voltage
2. Reheat Sensor Circuit
This circuit is composed of a part which transmits a change
of the reheat sensor voltage to PO0 terminal of LSI and of the
which supplies a constant current to the temperature sensi-
tive resistor RH.
When sensor cooking is started, 16 seconds of cleaning time
will follow to let out residual moisture.
After this cleaning time, the magnetron is oscillated. Forty se-
conds later, SW1 to SW5 in LSI are turned on so that the in-
put voltage to PO0 terminal of LSI will become approx. -4.8V.
Then, in compliance with the changes of vapor volume com-
ing from the food, the resistance ratio between RN and RH
varies to feed PO0 terminal of LSI with the voltage in propor-
tion to this ratio.
When this voltage level reaches the preset detection point, the
cooking is terminated.
if the initial voltage setting cannot be made due to open or
short-circuit the of sensor elements approximately 40 seconds
after the sensor cooking was started, the indicator shows ER-
ROR and sensor cooking is terminated.
ADVOl.
- 24”
f
-6.15V 34 P63
35
36 P9a
P91
- ‘9 PM)
1ooP 33b
6 rn4T
49 SW
49 SW2
4% SW3
49 SW4
47 sws
Figure T-l 0.
Figure T-9.
18

R-9370
INDICATOR CIRCUIT
Method of Display
Indicator element is Fluorescent Display.
Basically, a Fluorescent Display is a triode having a cathode,
a grid and an anode. Usually, the cathode of Fluorescent Dis-
play is directly heated and the filament serves as cathode.
When a proper voltage is applied to the filament to heat it,
thermo-electrons are emitted and, with positive voltage with
respect to filament being applied to the anode and grid, elec-
trons hit against the anode to illuminate the fluorescent body.
If the anode or grid voltage is zero or negative against the fila-
ment, thermo-electrons can not reach the anode, hence the
fluorescent body is not luminescent.
In this model, the Fluorescent Display B-digits, 13-segments
are used for displaying figures.
The Fluorescent Display employs the dynamic drive method,
when the high level of anode signal and grid signal agree, the
corresponding segment displays.
The foliowng signals are responstble for speclfylng segments
I Segment 1 sgnai / Segment I Sgnal /
Character format Its/-E-~ kE+G.
Indl-
MED P43
M-HIGH P43
HIGH P43
COMPCl WI3
AUTO PW
Kg Pm
COOK PSI I
Digure T-l 1. Indicator Circuit
19