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R1900M

5 – 2

Home

fuse

blows

when

power

cord

is

plugged

into

wall

receptacle

It

seems

that

the

output

power

is

lower

or

higher

than

the

rated

one.

"

.

"

does

not

appear

in

display

when

power

cord

is

first

plugged

into

wall

receptacle.

Oven

lamp

does

not

go

on

for

1

minute

after

door

is

opened.

Oven

lamp

and

antenna

motors

do

not

go

on

in

cook

cycle.

Oven

goes

into

a

cook

cycle

but

shuts

down

before

and

off

cooking

cycle.

Oven

does

not

go

into

cook

cycle

when

START

pad

is

touched.

Low

or

no

power

is

produced

during

cooking

condition.

(The

food

is

heated

incompletely

or

not

heated

at

all.)

Variable

cooking

does

not

operates

properly,

except

HIGH

power

functions.

Fan

motor

does

not

operate.

Exhaust

fan

does

not

operate.

Exhaust

motor

does

not

operate.

Oven

doen

not

go

into

cook

cycle

when

START

pad

on

the

door

is

touched.

OFF

CONDITION

CONDITION

PROBLEM

COOKING

CONDITION

POSSIBLE

CAUSE

A

ND

DEFECTIVE

PARTS

TEST

P

ROCEDURE

MAGNETRON(1),

(2)

POWERTRANSFORMER

(1),(2)

H.V.RECTIFIER

ASSEMBLY

(1),(2)

HIGHVOLTAGE

CAPACITOR(1),

(2)

SECONDARYINTERLOCK

SWITCH(1),

(2)

PRIMARYINTERLOCK

SYSTEM

DOORSENSING

SWITCH

MONITORSWITCH

(1),(2)

WEAKPOINT

(inNoise

filter)

MAGNETRONTEMP.

FUSE(1),

(2)

OVENTEMPERATURE

FUSE

OVENLAMP

OR

SOCKET

FANMOTORS

EXHAUSTFAN

EXHAUSTMOTOR

FUSEF10

(1),(2)

WEAKPOINTS

(forFan

motors)

WEAKPOINT

(forExhaust

fanm

otor)

EXHAUSTTHERMISTOR

MAGNETRONTHERMISTOR

NOISEFILTER

KEYUNITS

POWERUNIT

RELAYUNIT

CONTROLUNIT

SWITCHUNIT.

AIRFLOW

BLOCKED

LOOSEWIRING

SHORTIN

POWERSUPPLY

CORD

NOPOWER

AT

OUTLET

LOWPOWER

SUPPLYVOLTAGE

AB

C

D

E

F

F

G

J

KK

H

I

I

M

L

O

Q

R

P

N

Weak

point

(in

noise

filter)

blows

when

power

cord

is

p

lugged

into

wall

receptacle.

R1900M

5 – 3

SPECIFICATION OF ERROR

When a basic performance and the function are ruined

Displaying  and heating stop

EE0, EE1, EE2, EE3, EE8

When the dangers of the state of the high temperature and the ignition, etc. are 
foreseen

Displaying  and heating stop

EE7

When you mistake the setting of the heating time

Operation stop

EE9

When neither the power supply nor the environmental condition are proper

Operation stop

EE4, EE5, EE6

When informing of the exchange time of parts

Display Only

CC1, CC2, CC3, CC4



–

MG1 exchange time information

Using time of MG1

MG1



–

MG2 exchange time information

Using time of MG2

MG2



–

Exhaust Fan motor exchange time information Using time of Exhaust motor

Exhaust motor



–

T/C unit exchange time information

Using number of times of RY2/RY3

Relay unit

A

TEST PROCEDURE

POSSIBLE CAUSE

AND

DEFECTIVE PARTS

B D C E F H I K L M

R P S S T

EE0
EE0
EE0

EE0
EE0

EE0
EE0

EE1

EE1

EE2

EE2

EE3

EE3

EE3

EE4
EE5

EE6
EE6

EE60

EE7

EE7
EE7

EE8

EE8

EE8

EE8
EE8

EE8
EE8
EE8
EE8

EE9

Magnetron

1and

/or

2

Power

transformer

1

&

2

High

voltage

capacitor

1

and

/or

2

H.V.rectifier

assembly

1

and/or

2

Secondary

interlock

switch

1

a

nd/or

Primary

interlock

system

Fuse

12A

1

and/or

2

Weak

points

for

F

an

motors

(DC24V)

Magnetron

temp.

fuse

1

and/or

2

Magnetron

thermistor

1

and/or

2

Exhaust

thermistor

Fan

m

otors

Exhaust

motor

Antenna

motor

1

a

nd/or

2

Air

flow

blocked

Low

or

High

power

supply

voltage

No

load

or

small

load

operation

Loose

wiring

Exceeding

of

maxmum

cooking

time

Burned

food

Relay

unit

Control

unit

Antenna

sensor

(1)

(Upper)

Antenna

sensor

(2)

(Lower)

Microwave

sensor

Frequency

of

power

supply

is

high.

EE 1

Failer of high voltage circuit 1

EE 2

Failer of high voltage circuit 2

EE 3

Failer of high voltage circuit 1&2

EE 4

Too high of input voltage(+13%)

EE 5

Too low of input voltage(-13%)

EE 7

Food burned (temp., too high)

EE 8

Melted contacts of relays

EE 9

Over maximum cooking time

EE 10

EEPROM error

EE 11

Life end of magnetron 1

EE 21

Life end of magnetron 2

EE 31

Life end of magnetron 1&2

EE 81

Life end of relays RY2/RY3

EE 83

Over Current error

EE 14

MG1 Cooling Fan lock judge

EE 24

MG2 Cooling Fan lock judge

EE 44

Exhaust motor lock judge

EE 54

Life end of exhaust motor

EE 15

MG1 antenna rotation error

EE 25

MG2 antenna rotation error

EE 35

MG1/2 antenna rotation error

EE 16

MG1 thermistor open

EE 26

MG2 thermistor open

EE 17

MG1 temperature, too high

EE 27

MG2 temperature, too high

EE 18

Magnetron 1

EE 28

Magnetron 2

EE 38

Magnetron 1& 2

EE 29

Exhaust thermistor open/short

EE 19

No food

EE 39
EE 60

Small food
Not correct frequency

Error history

display

Usual error

display

Content of error

R1900M

6 – 1

R1900M

Service Manual

 

CARRY OUT 3D CHECKS.

Isolate the magnetron from high voltage circuit by removing all leads connected to filament terminal.

To test for an open circuit filament use an ohmmeter to make a continuity test between the magnetron filament terminals, the meter should show a
reading of less than 1 ohm.

To test for short circuit filament to anode condition, connect ohmmeter between one of the filament terminals and the case of the magnetron (ground).
This test should be indicated an infinite resistance. If a low or zero resistance reading is obtained then the magnetron should be replaced.

The following test procedure should be carried out with the microwave oven in a fully assembled condition (outer case fitted). Microwave output power
from the magnetron can be measured by IEC test procedure, 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 (sec-
ond), approximately P x t/4.187 calorie is generated. On the other hand, if the temperature of the water with V(ml) rises  T (

°C) during this microwave

heating period, the calorie of the water is v x  T.

Measuring condition:

1) Container

The water container must be a cylindrical borosilicate glass vessel having a maximum material thickness of 3 mm and an outside diameter of
approximately 190 mm.

2) Temperature of the oven and vessel

The oven and the empty vessel are at ambient temperature prior to the start of the test.

3) Temperature of the water

The initial temperature of the water is (10

±1)°C

4) Select the initial and final water temperature so that the maximum difference between the final water temperature and the ambient temperature is

5

°C.

5) Select stirring devices and measuring instruments in order to minimize addition or removal of heat.

6) The graduation of the thermometer must be scaled by 0.1

°C at minimum and an accurate thermometer.

7) The water load must be (1000

±5) g.

8) “t” is measured while the microwave generator is operating at full power. Magnetron filament heat-up time is not included.

NOTE: The operation time of the microwave oven is “t + 3" sec. (3 sec. is magnetron filament heat-up time.)

Measuring method:

1) Measure the initial temperature of the water before the water is added to the vessel.

(Example: The initial temperature T1 = 11

°C)

2) Add the 1 litre water to the vessel.

3) Place the load on the centre of the shelf.

4) Operate the microwave oven at HIGH until the temperature of the water rises by a value  T of (10

±2)K.

5) Stir the water to equalize temperature throughout the vessel.

6) Measure the final water temperature. (Example: The final temperature T2 = 21

°C)

7) Calculate the microwave power output P in watts from above formula.

IMPORTANT:

   The formula is as follows;
           P x t / 4.187 = V x   T+ 0.55 x mc (T2-T0)                                   P (W) = 4.187 x V x  T / t + 0.55 x mc (T2-T0)/t
   Our condition for water load is as follows:
          Room temperature (T0) ......................... around 20°C                         Power supply Voltage ........................... Rated voltage
          Water load ........................................................1000 g                          Initial temperature (T1) .................................... 10±1°C
          Heating time ..................................................... 22 sec.                          Mass of container (mc) ...................................... 330 g
        T2 .................................................... Final Temperature               P = 190 x  T

R1900M

6 – 2

± 15% of the rated output power.

CAUTION: 1

°C CORRESPONDS TO 150 WATTS. REPEAT MEASUREMENT IF THE POWER IS INSUFFICIENT.

The power output of this oven is rated using the method specified by IEC 60705. Full details of how to curry out this procedure can be found in the
Sharp Technical Training notes which is available from Sharp Parts Centre (part number SERV-LITMW01).

These requirements make the procedure unsuitable for routine performance checks.

NOTE: The following test method gives an indication of the output power only, it cannot be used to establish the actual/rated output power. If the true

output power is required, then the IEC60705 test method must be used.

Alternative simplified method:

1. Place 2 litres of cold water (between 12

°C and 20°C) in a suitable container.

2. Stir the water and measure the temperature in 

°C. Note temperature as T1.

3. Place the container in the microwave and heat the water for 47 sec. on full power.

4. When the 47 sec. is completed, remove the container and stir the water. Note temperature as T2.

5. Calculate the output power using the following formula:

R.F. Power Output = (T2 - T1) x 190.

NOTE: The result from this test should be within the allowance of 2000cc alternative method. (

±10%).

This oven should be tested for microwave leakage on completion of any repair or adjustment, following the procedure described in the Sharp Techni-
cal Training notes (part number SERV-LITMW01). The maximum leakage permitted in BS EN 60335-2-25 is 50W/m

2

 (equivalent to 5W/m

2

), however

it is not normal to detect any significant leakage, therefore, any leakage which is detected should be investigated.

It is essential that only leakage detectors with current calibration traceable to National Physical Laboratories are used.

Suitable leakage detectors: CELTEC A100 / APOLLO X1

1. CARRY OUT 3D CHECKS.

2. Disconnect the leads to the primary winding of the power transformer. Disconnect the filament and secondary winding connections from the rest of

the HV circuitry. Using an ohmmeter, set on a low range, it is possible to check the continuity of all three winding. The following readings should be
obtained:

                  a.Primary winding -------------------- approximately 1.3 

Ω

                  b.Secondary winding --------------- approximately 76 

Ω 

                  c.Filament winding --------------------------- less than 1 

Ω

If the readings obtained are not stated as above, then the power transformer is probably faulty and should be replaced.

3. CARRY OUT 4R CHECKS.

          Room temperature ................................................................. To = 21

°C

          Initial temperature .................................................................. T1 = 11

°C

          Temperature after (22 + 3) = 25 sec. ...................................... T2 = 21

°C

          Temperature difference Cold-Warm .....................................  T1 = 10

°C

          Measured output power
          The equation is “P = 190 x  T" .................... P = 190 x 10

°C = 1900 Watts

WARNING: High voltages and large currents are present at the secondary winding and filament winding of the power transformer. It is 

1000g

1000g

1000g

Heat up for 25 sec.