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211M -

MICROWAVE OUTPUT POWER (IEC-705)

The power output of this oven is rated using the method specified by IEC-705.  Full details of how to carry out this
procedure can be found in the Sharp Technical Training notes which is available from Sharp Parts Centre
(part number SERV-LITMW01).

Using this procedure, the heating time to raise 1000g of water by 10

°

C is approximately 50 seconds.

The IEC-705 procedure must be carried out using laboratory-type procedures and equipment.  These requirements
make the procedure unsuitable for routing performance checks.  An indication of the power being produced by the oven
can however be obtained using the procedure given below.

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 2 minutes on full power.
4. When the 2 minutes is completed, remove the container and stir the water.  Note the water temperature as T2.
5. Calculate the output power using the following formula:

R.F. Power Output = (T2 - T1) x 70.

MICROWAVE LEAKAGE TEST

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

2 

(equivalent to 5mW/cm

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 the National Physical Laboratories are used.

Suitable leakage detectors :

CELTEC A100
APOLLO X1

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211M -

The control panel consists of circuits including semiconductors such as LSI, ICs, etc. Therefore, unlike conventional
microwave ovens, proper maintenance can not be performed with only a voltmeter and ohmmeter.
In this service manual, troubleshooting by replacement is described according to the symptoms indicated.
1. Control Panel

The following symptoms indicate a defective control unit.

1-1  In connection with LEDs

a) At a certain LED, all or some LEDs do not light up.
b) At a certain LED, brightness is low.
c) Only one LED does not light up.
d) All or some LEDs continue to light up.
e) A certain group of LEDs do not light up.
f) The LEDs flicker.

1-2  Other possible troubles caused by defective control unit.

a) Buzzer does not sound or continues to sound.
b) Cooking is not possible.
c) Cooking time can not be set.
d) Power level can not be set.

CARRY OUT 3D CHECKS.

Remove the outer case and check voltage between Pin Nos. 3 and 5 of the 3 pin connector (A)  on the control unit with an
A.C. voltmeter.
The meter should indicate 230-240 volts, if not check oven circuit.

Relay Test
Check voltage at the relay coil with a D.C. voltmeter during the microwave cooking operation. convection cooking operation
or grill operation.

DC. voltage indicated ............. Defective relay.
DC. voltage not indicated ....... Check diode which is connected to the relay coil. If diode is good, control unit is defective.

RELAY SYMBOL

OPERATIONAL VOLTAGE

CONNECTED COMPONENTS

RY1

Approx. 12.0V D.C.

Oven lamp / Turntable motor / Fan motor

RY2

Approx. 12.0V D.C.

High voltage transformer

CARRY OUT 4R CHECKS.

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211M -

To protect the electronic circuits, this model is provided with a fine foil pattern added to the input circuit on the PWB, this foil
pattern acts as a fuse. If the foil pattern is open, follow the troubleshooting guide given below for repair.
Problem: POWER ON, indicator does not light up.

CARRY OUT 3D CHECKS.

STEPS

OCCURRENCE

CAUSE OR CORRECTION

1

The rated AC voltage is not present at

Check supply voltage and oven power cord.

Power terminal of CPU connector (CN-A).

2

The rated AC voltage is present at primary

Low voltage transformer or secondary circuit defective.

side of low voltage transformer.

Check and repair.

3

Only pattern at "a" is broken.

*Insert jumper wire J1 and solder.

(CARRY OUT 3D CHECKS BEFORE REPAIR)

4

Pattern at "a" and "b" are broken.

*Insert the coil RCILF2003YAZZ between "c" and "d".

(CARRY OUT 3D CHECKS BEFORE REPAIR)

NOTE: *At the time of these repairs, make a

visual inspection of the varistor for burn-
ing damage and examine the transformer
with tester for the presence of layer short
circuit (check primary coil resistance).
If any abnormal condition is detected,
replace the defective parts.

CARRY OUT 4R CHECKS.

(J1)

VRS1

CN - A

S

P

15

8

211M -

Control Unit
Control unit consists of LSI, power source circuit, synchro-
nizing signal circuit, ACL circuit, buzzer circuit, encoder
circuit, indicator circuit and potentiometer circuit.

This LSI controls the encoder signal, potentiometer
signal, relay driving signal for oven function, buzzer
signal and LED signal.

This circuit generates voltage necessary in the control
unit.

Symbol

Voltage

Application

VC

-5.0V

LSI(I-1)

VR

-12.0V

RELAY(RY1,2)

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.

A circuit to generate a signals which resets the LSI to
the initial state when power is supplied.

The buzzer is responsive to signals from the LSI to
emit audible sounds (key touch sound and
completion sound).

A switch to "tell" the LSI if the door is open or closed.

To drive the magnetron, heating element, fan motor,
turntable motor and  light the oven lamp.

The encoder generates the pulse signal, and the
pulse signal is sent to the LSI.

Indicator elements are the Light-emitting diodes
(LD1-LD24).

The circuit makes setting of the power level by
variable resistance.

OUTLINE OF CONTROL PANEL