Sharp R-7280 User manual

R-7280

R-1720

SHARP SERVICE MANUAL

S6703R7280J//

MICROWAVE OVEN

MODELS R-7280

R-l 720

Photo R-7280 in the interests of user-safety the set should be restored to its original

condition and only parts identical to those specified should be used.

( RD16101 U)

TABLE OF CONTENTS

FOREWORD Page

.............*.....*...........*................*...................................................................................................... I

CAUTION, MICROWAVE RADIATION ...................................................................*...........................*.......... 1

PRODUCT DESCRIPTION ............................................................................................*.......*.......................... 2

OPERATION .....................................................I................................................................................................. 4

SERVICING .................................................................................*...................................................................... 7

TOUCH CONTROL PANEL ASSEMBLY .......................*............................................................................. 14

COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE ....................................................... 21

MICROWAVE MEASUREMENT PROCEDURE .......................................................................................... 25

PICTORIAL DIAGRAM .................................................................................................................................. 26

CONTROL PANEL CIRCUIT ....................................................a.........a..............,.....a..................................... 27

PRINTED WIRING BOARD ............................................................~.............................................................

PARTS LIST 28

*........................................................................................................,.......................................... 29

PACKING AND ACCESSORIES ................................................................................................................... 36

SHARPCORPORATION

R -7280

R -1720

__- “-- -“-.-1_ “““1.1-“111

“i

” ..” ”

r-A--- .. . .... ...... ’ - ..... .... ./-- ...- .... .N ...... _ .

Photo R-l 720

R-7280

R-1720

SERVICE MANUAL

MICROWAVE OVEN

R-7280/ R-1720

FOREWORD

This Manual has been prepared to provide Sharp Corp. Service

Personnel with complete Operation and Service information for

the SHARP MICROWAVE ovens, R-7280/ R-1720.

It is recommended that service personnel carefully study the

entire text of this manual so they will be qualified to render

satisfactory customer service.

Check interlock switches and door seal carefully. Special at-

tention should be given to avoid electrical shock and microwave

radiation hazard. (RD36102U)

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 device without

a microwave energy absorbing load attached. Never look into

an open waveguide or antenna while the device is ener ized.

(1 036201 U)

SHARPCORPOf?ATK)N

OSAKA, JAPAN (RD

37201 U)

R -7280

R-l 720

PRODUCT DESCRIPTION

EXPLANATION OF MICROWAVE COOKING

The Sharp Microwave Oven uses microwave energy to

produce heat in the food to be cooked. Unlike con-

ventional ovens microwave energy will cook foods

without applying external heat.

moisture content, like most foods, will absorb micro-

wave energy. As the microwave energy at a frequency

of 2450 Megahertz enters the food, the molecules align

themselves with the energy. Because the microwaves

are changing polarity every half cycle, the food mole-

Microwaves, which are short electromagnetic waves

of RF (radio frequency) energy, pass through materials

such as glass, paper, china and most plastics. Materi-

als such as metal and aluminum foil tend to reflect

microwaves and may be used only as recommended in

cules are changing direction every half cycle or oscil-

lating back and forth 4,900,000,000 times per second.

This high speed oscillation causes friction between the

molecules, thereby converting the microwave energy

to heat. (RD41101U)

the cooking instructions. Materials with a high

SPECIFICATION

ITEM I DESCRIPTION

Power Requirements / 240 Volts

i 50 Hertz

/ Single phase, 3 wire earthed

j 13oow - -___

Power Consumption -___ - --

Power Output ~~-~650 watts nominal ofRF microwave energy (2 liter water load)

j Operating frequency of 2450MHz

-______ -- -__

Case Dimensions I

, Width 520 mm

/ Height 318 mm including foot

’ Depth 393 mm

------- -~-~

Cooking Cavity Dimensions Width 345 mm

- --__

Control Complement

1 Height 217 mm

1 Depth 364 mm _-__---__- -____-

i Touch Control System

! Timer (0 - 99 min 99 sec. )

: Microwave Power for Variable Cooking

I Repetition Rate;

/ HIGH ............................... Full power throughout the cooking time

/ MED HIGH ............................................ approx. 70% of Full Power

1 MED ....................................................... approx. 50% of Full Power

MED LOW DEFROST .......................... approx. 30% of Full Power

/ LOW ....................................................... approx. 10% of Full Power

INSTANT COOK/START COOKING

1 AUTO START COOKING

/ EASY DEFROST

j EASY REHEAT

/ MORE/LESS pad

- Set Weight -- 1 Approx. 17.5 kg

(RD44101

NOTE: Numbers and leters shown after sentences such as “RD44101 U” are for factory use only.

R-7280

R-l 720

OVEN DIAGRAM

1. Ventilation openings

2. Oven lamp

3. Oven door with see through window

4. Removable turntable

5. Roller Stay

Auto-TouchTM Control Panel

1 Dinner plate 1-2plates

3 CasserolelSuup I-dcups

7 II nMEDLOWIIt-

8 11 nMED I /I

&~++jq,

f If \

INSTANT COOK

/ ::.fii3 j( START /A

-- I-

k:---./ i

/ 1

2 6

11.

Door latches

Door open button

Auto-Touch Control Panel

Digital readout

Waveguide cover

Access cover for oven lamp replacement

Door hinges

NUMBER PADS

EASY REHEAT PAD

EASY DEFROST PAD

VARIABLE COOKING CONTROL PADS

MORE ( A 1, LESS ( v ) PADS

AUTO START/CLOCK PAD

TIMER/HOLD PAD

INSTANT COOK/START PAD

STOP/CLEAR PAD

R-7280

R-1720

COOKING CONDITION

HIGH COOKING CONDITION

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:

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 oven lamp/turntable motor/fan motor

RY-2 power transformer

240 volts A.C. is supplied to the primary winding

of the power transformer and is converted to about

3.5 volts A.C. output on the filament winding, and

approximately 1900 volts A.C. on the high voltage

winding.

The filament winding voltage heats the magnetron

filament and the H.V.

voltage doubler circuit. winding voltage is sent to a

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.

Upon completion of the cooking time, the power

transformer, oven lamp, etc. are turned off, and the

generation of microwave energy is stopped,

oven will revert to the OFF condition. The

OPERATION

DESCRIPTION OF OPERATING SEQUENCE

The following is a description of component functions

during oven operation. (RD71101U)

OFF CONDITION

Closing the door activates both door latch switches:

upper latch switch and lower latch switch. (In this

condition, the monitor switch contacts are opened.)

The stop switch is activated by the latch head.

When oven is plugged in, 240 volts AC. is supplied to

the control unit.

But no components in the oven will operate.(Figure

o-1 .)

Note: When the door is opened by pushing the door

open button, the contacts of the relay RY-1 are

1. closed, then the oven lamp lights.

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.

6. When the door is opened during a cook cycle,

monitor switch, upper latch switch and lower latch

switch are activated with the following results. The

circuits to the turntable motor, the cooling fan mo-

tor, and the high voltage components are deener-

gized, the oven ‘lamp remains on, and the digital

readout displays the time still remaining in the cook

cycle when the door was opened.

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.

When the door opens from a closed position,

the stop switch, upper and lower latch switches

first operate to open their contacts, and then

the monitor switch contacts close.

When the door is closed from the open posi-

tion, the monitor switch contacts first open,

and then the contacts of the stop switch, upper

and lower latch switches close.

case the upper latch switch fails with its contacts

closed when the door is opened, the monitor switch

will form a short circuit through the monitor fuse, and

the upper latch switch, causing the monitor fuse to

blow.

MED HIGH, MED, MED LOW DEFROST, LOW

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 30 sec-

ond time base. Microwave power operation is as fol-

lows:

-- VARI-MODE

HIGH

(100% power)

MED HIGH

(approx. 70wpower)

MED

(approx. 50% power)

MED LOW DEFROST

(approx. 30% power)

LOW

(approx. 10% power)

ON TIME OFF TIME

32 sec. -2 sec.

24 sec. 6 sec.

18 sec. 12 sec.

12 sec. 18 sec.

6 sec. 24 sec.

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)

R-7280

R-l 720

z 2

y3”aog

ow&Jo-

,gt--%~~a

O_iU SW-la:0

zogp$dgn~

OEX”5k&”

0 ~OOOUZa3

,oouaoI-0

pOL>OW-

I O--N C-Y u

W W

I &

: 2

I I

$2 =,a$=yy-

?I 5wg,zvr,cJ

:2x;ezpz g:;

6tS r----’

I I--dGl +

’ -B

j i ,,Yi17

.:$

II I 14 i,,Q [

E$P

r-3--L--

I-i

M 68ffi i;s’ ~~

IEI g

g 2,

iY3a -72 ”J

EL ;

ri B

E :

r- 1 5

EL-

31 8 --- G 3 ;:

s ,w I

24LIZ

mv)

2 tg

on<

L&p

00&Q

z-‘ak

0” x2

0 Egg”

I= no_12

ZCIUO

$ 0-m

I” F

2 is

r---j

L--l

&ii

R-7280

R-1720

DESCRIPTION AND FUNCTION OF COMPONENTS ,

UPPER LATCH SWITCH

The switch is activated by the upper latch head on the

door while the door is closed.

When the door is opened, the switch interrupts the

circuit (except oven lamp).

LOWER LATCH SWITCH

The switch is activated by the lower latch head on the

door. When the door is opened, the switch interrupts

the circuit to transformer. A cook cycle cannot take

place until the door is firmly closed and the INSTANT

COOK/START pad touched.

STOP SWITCH

The stop switch is located on latch hook and activated

by the lower latch head and switch lever. When the

open button is depressed while the oven is in cook

cycle, the stop switch contacts open to de-energize the

relay( RY-1 ) and relay( RY-2) circuits in the control and

causes cook time count down to pause.

MONITOR SWITCH

The monitor switch is activated (the contacts of “NC”

opened) by the upper latch head on the door while the

door is closed. The switch is intended to render the

oven inoperative by means of blowning the monitor

fuse when the contacts of the upper latch switch fail

to open when the door is opened.

Functions:

1. When the door is opened, the monitor switch

normal close contacts (to the ON condition) due

to their being normally closed. At this time the

upper latch switch is in the OFF condition (con-

tacts open) due to their being normally open con-

tact switch.

2. As the door goes to a closed position, the monitor

switch normal close contacts are first opened and

then the upper latch switch contacts close and

lower latch switch contacts, (On opening the door,

each of these switches operate inversely.)

3. If the door is opened, and the upper latch switch

contacts fail to open, the monitor fuse blows si-

multaneously with closing of the monitor switch

contacts.

CAUTION:BEFORE REPLACING A BLOWN MONI-

TOR FUSE, TEST THE UPPER LATCH FOR

PROPER OPERATION. (REFER TO CHAP-

TER “TEST PROCEDURE”).

DOOR OPEN MECHANISM

The door can be opened by pushing the open button

on the control panel, refer to the Figure D-l.

When the open button is pushed, the cook switch lever

on the latch hook is moved upward, operating the latch

head. The latch head is moved upward, and released

from the latch hook. Now, the door can be opened.

OVEN LAMP

The oven lamp illuminates the interior of the oven so

that food being cooked can be examined visually

through the door window without having to open the

door.

COOLING FAN MOTOR

The cooling fan motor drives a blade which draws

cooling air through the back vents.

This cooling air is directed through the air vanes sur-

rounding the magnetron and cools the magnetron.

This air is channeled through the oven cavity to remove

steam and vaports given off from the heating foods.

It is then exhausted at the back of the oven cavity.

MAGNETRON TEMP. FUSE

The temp. fuse located on the oven cavity is designed

to prevent damage to the magnetron if an overheated

condition develops in the tube due to cooling fan fail-

ure, obstructed air ducts, dirty or blocked air intake, etc.

Under normal operation, the temp. fuse remains closed.

However, when abnormally high temperatures are

reached within the magnetron, the fuse will open,

causing the oven to shut down.

This is a fuse and it does not reset.

OVEN TEMP. FUSE

When foods in oven cavity fire, oven temperature fuse

stops ventilating from fan motor and extinguishes fire

in oven cavity before fire goes outside the unit,

MONITOR

SWITCH

UPPER

LATCH

SWITCH

LOWER

LATCH

SWITCH

BUTTON

Figure D-1. Latch Switches Adjustment

R-7280

R-1720

SERVICING

TROUBLESHOOTING GUIDE

When troubleshooting the microwave oven, it is helpful to

follow the Sequence of Operation in performing the checks.

Many of the possible causes of trouble will require that a

specific test be performed. These tests are given a procedure

letter which will be found in the “Test Procedures section.*’

IMPORTANT: If the oven becomes inoperative because of a

blown fuse in the monitor-upper latch switch

circuit, check the monitor switch and upper

latch switch before replacing the fuse.

PROBLEM - POSSIBLE CAUSE TEST PROCEDURE OR

CORRECTION 4

Home fuse blows when power cord

is plugged into wall receptacle.

Oven fuse blows when power cord

is plugged into wall receptacie.

” 88:88 ” does not appear in display

when power cord is first plugged

into wail outlet.

Display does not operate properly

when STOP/CLEAR key is touched.

(Buzze should sound and time of

day should uppar in display.)

Oven lamp does not light with

door opened.

OFF CONDITION

Shorted wire in power cord or wire harness.

Shorted wire in power cord or wire harness,

Oefective monitor switch.

NO power at outlet.

No power from service entrance.

Open wire in power cord or wire harness.

Blown fuse.

Defective temp. fuse.

(magnetron and oven)

Open wire In power cord, wrrmg harness,

or wrring between control panel assembly

unrts.

Replace cord or check wiring.

Replace power cord or check

and repair wire harness.

Procedure H.

Check home fuse.

Check wall outlet.

Replace same or repair wiring.

Procedure I.

Procedure G.

Replace or reparr wiring.

Defective controi unit. Procedure J.

Defective key untt. Procedure J.

Defective stop switch. Procedure F.

Defective control unit. Procedure J.

Defective oven lamp. Replace oven lamp.

Defective stop switch. Procedure F.

Defective control unit. Procedure J.

Open or loose wire connection to the above Check wiring.

components.

COOKING CONDITION

Oven lamp does not light in cook

cycle.

(Do light when door is opened.)

Defective relay RY-1 on control unit. Procedure J.

R-7280

R-1720

TROUBLESHOOTING GUIDE (CONT’D)

PROBLEM POSSIBLE CAUSE TEST PROCEDURE OR

CORRECTION

COOKING CONDITION (CONT’D)

Oven lamp does not light at all.

Cook indicator appears in display but

turntable motor does not operate.

Burned out bulb.

Open wiring to oven lamp socket.

Defective relay RY-1 on control unit.

Turntable motor defective.

Replace oven lamp.

Check and repair wiring.

Procedure J.

Replacemotor.

Open or loose wiring between control

unit and motor. Check and repair wiring.

Oven lamp lights but fan motor

does not operate.

(Turntable motor does operate)

Defective fan motor. Procedure E.

Open or loose wiring to fan motor. Check and repair wiring.

Oven does not go into cook cycle

when INSTANT COOK/START

key is touched.

Upper and Lower latch switches and STOP

switch defective or out of adjustment.

Blown Fose

Procedure F.

Procedure I.

I Defective temp. fuse. (Magnetron and Oven) I Procedure G. 1

I Defective relay RY-1, RY-2 on control unit. Procedure J. 1

Defective control unit.

Defective key untt.

Open or loose wiring to the above

components.

Defective magnetron.

Defective relay RY-2 on control unit.

Defective power transformer.

Defective rectifier.

Defective high voltage capacitor.

Procedure J.

Check and repair wiring.

Procedure A.

Procedure J.

Procedure 8.

Procedure C.

Procedure 0.

Oven seems to be operating but

little or no heat is produced in

oven load. (Food incompletely

cooked or not cooked at all at end

of cook cycle)

I t 1 I

I Defective control unit. I Procedure J. I

Open or loose wiring to the above

components. Check and repair wiring.

Oven goes into a cook cycle but

extremely uneven heating is

produced in oven load (food).

Turntable motor does not operate. Replace turntable motor.

Oven does not cook properly when

cooking control set to LOW, MED

LOW, MED, MED HIGH cooking

powers.

(Operates properly on HIGH.)

Defective control unit.

Defective key unit.

Open or loose wiring between the above

components.

Procedure J.

Check and repair wiring.

R-7280

R-1720

PROBLEM POSSIBLE CAUSE TEST PROCEDURE OR

CORRECTION

EASY DEFROST condition touching Programmed incorrectly

INSTANT COOK/START Pad, EASY DEFROST wile only operate

“ERROR” appears. on a specific weight.

Range for each food category.

See staps for Easy Defrosy is

Operation Manual.

AH sensor open and/or short.

Defective control unit.

Procedure 0.

Procedure J.

R -7280

R-1720

TEST PROCEDURES

PROCEDURE

LETTER COMPONENT TEST

A MAGNETRON ASSEMBLY TEST

DlSCHARGE THE HIGH VOLTAGE CAPACITOR BEFORE TOUCHING ANY OVEN COMPO-

NENTS OR WIRING.

To test for an open filament, isolate the magnetron from the high voltage circuit. A continuity

check across the magnetron filament leads should indicate less than 1 ohm.

To test for a shorted magnetron, connect the ohmmeter leads between the magnetron fiiament

leads and chassis ground. This test should indicate an infinite resistance. If there is little or no

resistance, the magnetron is grounded and must be replaced.

Power output of the magnetron can be measured by performing a water temperature rise test.

This test should only be used if above rests do not indicate a faulty magnetron and there is no

defect in the following components or wiring: rectifier, high voltage capacitor, heater transformer

and power transformer.

MICROWAVE OUTPUT POWER

Microwave output power from the magnetron can be measured by way of substitution, i.e. it can

be measured by using water load how much it can be absorbed by the water load. To measure

the microwave output power in the microwave oven, the relation of calorie and watt is used.

When P(W) heating works for t(second), approximately P x t/4.2 calorie is generated. On the

other hand, if the temperature of the water with V(ml) rises AT ( “C) during this microwave

heating period, the calorie of the water is V x AT.

The formular is as follows;

P x t / 4.2 =Vx AT

P (W) = 4.2 x V x AT/t

Our condition for the water load is as follows:

Water load ... 2000 ml, Heating time ...I 27 seconds

P = 66 x AT

Measuring method;

1. Put the water load of two (2) litres on the center of the oven shelf. The water load should

be arranged in two (2) Pyrex beakers, the size of which is one (1) litre, and be placed at right

and left, side by side, on the oven shelf.

2. Measure the temperature of water before heating and also after heating during 127 seconds

by microwave, and calculate the temperature rise. The temperature rise should be the average

of temperature differences measured in each beaker.

3. The output power should be calculated as follows. In case the measuring result is not satis-

factory, execute the measurement several times and judge the result from the synthetic point

of view. Microwave output power should be within + 15% of the nominal one.

Calculation of output power;

Microwave output power ...P(W)=66x AT(X)

AT = ( ATL + ATR) / 2 : average temperature rise

ATL = (TL2 - TLI), ATR = (TR2 - TRl)

TL2 : water temperature after heating in left beaker

TLl : water temperature before heating in left beaker

TR2 : water temperature after heating in right beaker

TRI : water temperature before heating in right beaker

Measuring condition;

As the microwave output is affected by several conditions, the measurement should be made

carefully with following attentions.

I. Initial temperature of salt water should be IO + 1 “C. (The salt water should be contained

bon (1) percent of salt.) Well and quickly stir the water and the temperature measurement

should be done immediately after heating.

2. The graduation of thermometer should be scaled by 0.1 “C at minimum and an accurate mer-

cury thermometer is recommended.

R-7280

R-1720

TEST PROCEDURES (CONT’D)

PROCEDURE

LE-ITER COMPONENT TEST

4. Room temperature should be around 20 “C.

5. Power supply voltage should be specification voltage.

POWER TRANSFORMER TEST

DISCHARGE THE HIGH VOLTAGE CAPACiTAOR BEFORE TOUCHING ANY OVEN COMPO-

NENTS OR WIRING.

Disconnect the primary input terminals and measure the resistance of the transformer with an

ohmmeter. Check for continuity of the coils with an ohmmeter. On the R x 1 scale, the resistance

of the primary coil should be less than 1.47 ohms and the resistance of the high voltage coil

should b approximately 100 ohms; the resistance of the filament coil should be less than 1 ohm.

(HIGH VOLTAGES ARE PRESENT TO HIGH VOLTAGE TERMINAL, SO DO NOT ATTEMPT TO

MEASURE THE FILAMENT AND HIGH VOLTAGE.)

C SILICON RECTIFIER TEST

DISCHARGE THE HIGH VOLTAGE CAPACITOR BEFORE TOUCHING ANY OVEN COMPO-

NENTS OR WIRING.

Isolate the rectifier from the circuit. Using the highest ohm scale of the meter, read the resistance

across the terminals and observe, reverse the leads to the rectifier terminals and observe meter

reading. If a short is indicated in both directions, or if an infinite resistance is read in both di-

rections, the rectifier is probably defective and should be replaced. (R082501 U\

D HIGH VOLTAGE CAPACITOR TEST

DISCHARGE THE HIGH VOLTAGE CAPACITOR BEFORE TOUCHING ANY OVEN COMPO-

NENTS OR WIRING.

If the capacitor is open, no high voltage will be available to the magnetron. Disconnect input

leads and check for short or open, between the terminals using an ohmmeter.

Checking with a high ohm scale, if the high voltage capacitor is normal, the meter will indicate

continuity for a short time and should indicate approximately 10M R once the capacitor is

charged. If the above is not the case, check the capacitor with an ohmmeter to see if it is shorted

between the terminals. If it is shorted, replace the capacitor. (RD82603U1 ,

E SWITCH TEST

Isolate the switch and check the contacts by using an ohmmeter using the following table.

If improper operation is indicated, make the necessary switch adjustment or replacement.

Table: Switch Connection

Connection i Common Tekknal- Normally Open Terminal

I (COM) (NOI Common Terminal-Normally Close Terminal

(COM) )

Operation (NC) I

! /

Plunger released i ,

Open circuit Close circuit

1 Plunger pushed j Closed circuit Open circuit ------i

(RD82701 U)

R-7280

R-1720

TEST PROCEDURES (CONT’D)

PROCEDURE

LETTER COMPONENT TEST

F MAGNETRON AND OVEN TEMP. FUSE TEST

A continuity check across the temp. fuse terminals should indicate a closed circuit unless the

temperature of the temp. fuse reaches approximately 145 “C.

An open magnetron temp. fuse indicates overheating of the magnetron assembly. if the temp.

fuse indicates a open circuit, replace the temp. fuse and check for restricted air flow to the

magnetron through the opening in the chassis, especially the air duct and fan motor.

An open oven temp. fuse indicate overheating of oven cavity.

If the oven temp.fuse indicates aopen circuit, replace the oven temp.fuse and check the reason

of the oven heating and check the wiring etc.

MONITOR SWITCH TEST

Before performing this test, make sure that the upper latch switch is operating properly referring

to the above Switch Test Procedure.

Disconnect the wire lead from the monitor switch (NC) terminal.

Check the monitor switch operation by using the ohmmeter as follows.

When the door is open, the meter should indicate a closed cirqit.

When the monitor switch actuater is pushed by a screw driver through the lower latch hole on

the front plate of the oven cavity with the door opened (in this condition the plunger of the

monitor switch is pushed in), the meter should indicate an open circuit.

If improper operation is indicated, the switch may be defective.

After testing the monitor switch, re-connect the wire lead to the monitor switch (NC) terminal

(RD82803U)

UPPER

LATCH

SWITCH

WHITE

BLUE

MONITOR

ry NO CO&l

OHMMETER

MONITOR

SWITCH

UPPER

LATCH

SWITCH

LOWER

LATCH

SWITCH

_-STOP

SWITCH

. SWITCH

LEVER

BLOWN OVEN FUSE

If the oven fuse in the upper latch switch-monitor switch circuit is blown when the door is

opened, check the upper latch switch and monitor switch before replacing the blown fuse.

If the oven fuse is blown by improper switch operation, replace the defective switch and oven

fuse at the same time.

Replace just the oven fuse if the switches operate normally.

CAUTION; REPLACEMENT FUSE MUST BE THE LISTED FUSE IN PARTS LIST.

R-7280

R-l 720

TEST PROCEDURES (CONT’D)

PROCEDURE

LETTER COMPONENT TEST

I TOUCH CONTROL PANEL ASSEMBLY TEST

The touch control panel consists of circuits including semiconductors such as LSI, KS, etc.

Therefore, unlike conventional microwave ovens, proper maintenance cannot be performed with

only a voltmeter and ohmmeter. Troubleshooting by unit replacement is described according to

the symptoms indicated.

Control Unit

The following symptoms indicate a defective control unit. Replace the control unit.

1. In connection with pads.

a) When touching the pads, a certain group of pads do not produce a signal.

b) When touching the pads, no pads produce a signal.

2. In connection with indicators

a) At a certain digit, all or some segments do not appear.

b) At a certain digit, brightness is low when it appears.

c) Only one indicator does not appear.

d) The corresponding segments of all digits do not appear; or they continue to appear.

e) Wrong figure appears.

f) A certain group of indicators do not appear.

g) The figure of all digits flicker.

3. Other possible troubles caused by a defective control unit.

a) Buzzer does not sound or continues to sound.

b) Cooking is not possible.

R-7280

R-1720

TOUCH CONTROL PANEL ASSEMBLY I

OUTLINE OF TOUCH CONTROL PANEL

The touch control section consists of the following

units as shown in the touch control panel circuit.

(1) Key Unit

(2) Control Unit

The principal functions of these units and the signals

communicated among them are explained below.

(RD911A3U)

Key Unit

The key unit is composed of a matrix, signals generated

in the LSI are sent to the key unit through P62, P63

and P70-P73.

When a key pad is touched, a signal is completed

through the key unit and passed back to the LSI

through PIO-PI 3 to perform the function that was re-

quested.

Control Unit

Control unit consists of LSI, power source circuit,

synchronizing signal circuit, ACL circuit, buzzer circuit

and indicator circuit. (RD915Bl U)

LSI

This LSI controls the key strobe signal, relay driving

signal for oven function and indicator signal.

(RD916Al U)

Power Source Circuit

This circuit generates voltage necessary in the

control unit.

Symbol Voltage Application

VDD -12v

VREF LSI (lC1 ), ACL circuit

VP -6.15V LSI (ICI)

-29V Fluorescent display tube : Grid

VF+ -18V and anode voltage

Filament of fluorescent display

tube

VF- -2lV

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 commercial frequency. (RD918Al U)

ACL Circuit

A circuit to generate a signal which resets the LSI

to the initial state when power is supplied. (RD919Al U)

Buzzer Circuit

The buzzer is responsive to signals from the LSI

to emit noticing sounds (key touch sound and

completion sound). (RD91 AA1 U)

Stop Switch

A switch to “tell” the LSI if the door is open or

closed. (RD91 BA2U)

Relay Circuit

To drive the magnetron, fan motor, turntable motor

and light’the oven lamp. (RD91 CB2U)

Indicator Circuit

Indicator element is a Fluorescent Display.

Basically, a Fluorescent Display is triode having a

cathode, a grid and an anode. Usually, the cathode

of a Fluorescent Display is directly heated and the

filament serves as cathode.

The Fluorescent Display 6-digits, 13-segments are

used for displaying figures. (RD91 DA1 U)

R-7280

R-1720

DESCRIPTION OF LSI

LSI(IZA086DR)

The I/O signal of the LSI(IZA086DR) is detailed in the following table. (RD93101 U)

PIN NO. j 1-4 1 SIGNAL / P30-P33 I I/O / OUT

Seament data sianals.

Refer to the touch control panel circuit for the relationship between signals and indicators.

Normally, one pulse is output in every synchronized signal period, and input to the anode of the fluorescen;t$,$sl;

PIN NO. / 5 1 SIGNAL ! ACL I I/O 1 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. (RD93MA2U)

PIN NO. 1 6 1 SIGNAL ( CL1 I l/O 1 IN

Internal clock oscillation frecluencv input settinq.

The internal clock frequency is set by inserting the ceramic filter oscillation circuit with respect to CL2 terminal.

(RD93EA2U)

PIN NO. / 7 1 SIGNAL / CL2

Internal clock oscillation freauencv control output.

Output to control oscillation input of CL1 .

I I/O / OUT

(RD93EAl U)

PIN NO. / 8 1 SIGNAL / P40 I I/O / OUT

Seament data sianal.

Signal similar to P30. (RD939A2U)

PIN NO. / 9 1 SIGNAL / TEST I I/O i IN

Terminal not used. Connected to VDD. (RD93KA4U)

PIN NO. 1 lo-13

Secrment data signal.

Signal similar to P30.

1 SIGNAL j P41-P43,P50 I l/O 1 OUT

.( RD939A2U)

PIN NO. i 14 1 SIGNAL / P51 I I/O / IN

Terminal to chanae functions accordinrr to the model.

Signal in accordance with the model in operation is applied to set up its function.

Terminal not used. (Rd93JAl U)

PIN NO. / 15

Terminal not used. 1 SIGNAL 1 P52 I I/O ) IN

(RD93KA2U)

R-7280

R-1720

PINNO. j 16 1 SIGNAL / P53 I l/O 1 IN

Terminal for manufacture test.

Normally terminal not used. (RD93lA3U)

PIN NO. / 17,18

Terminal not used. 1 SIGNAL j P6O,P61 I I/O j IN

(RD93KA2U)

PINNO. j 19 1 SIGNAL / P62 I I/O j OUT

Key strobe sianal.