Sharp R-770B Service Manual download pdf (Page 28)

R-770B

MICROWAVE MEASUREMENT

After adjustment of door latch switches, monitor switch

and door are completed individually or collectively, the

following leakage test must be performed with a survey

instrument and it must be confirmed that the result meets

the requirements of the performance standard for micro-

wave oven.

REQUIREMENT

The safety switch must prevent microwave radiation emis-

sion in excess of 5mW/cm

at any point 5cm or more from

external surface of the oven.

PREPARATION FOR TESTING:

Before beginning the actual test for leakage, proceed as

follows;

1. Make sure that the test instrument is operating nor-

mally as specified in its instruction booklet.

Important:

Survey instruments that comply with the requirement

for instrumentations as prescribed by the performance

standard for microwave ovens must be used for test-

ing.

Recommended instruments are:

NARDA 8100

NARDA 8200

HOLADAY HI 1500

SIMPSON 380M

2. Place the oven tray into the oven cavity.

3. Place the load of 275 ± 15ml of water initially at 20

± 5˚C in the centre of the oven tray. The water

container should be a low form of 600 ml beaker with

inside diameter of approx. 8.5cm and made of an

electrically non-conductive material such as glass

or plastic.

The placing of this standard load in the oven is impor-

tant not only to protect the oven, but also to insure that

any leakage is measured accurately.

4. Close the door and turn the oven ON with the timer set

for several minutes. If the water begins to boil before

the survey is completed, replace it with 275ml of cool

water.

5. Move the probe slowly (not faster that 2.5cm/sec.)

along the gap.

6. The microwave radiation emission should be meas-

ured at any point of 5cm or more from the external

surface of the oven.

mW cm

Microwave leakage measurement at 5 cm distance

SHARP

used to assure compliance with proper micro-

wave radiation emission limitation standards.

(Refer to Microwave Measurement Procedure.)

After any service, make sure of the following :

1. Door latch heads smoothly catch latch hook through

latch holes and that latch head goes through centre of

latch hole.

2. Deviation of door alignment from horizontal line of

cavity face plate is to be less than 1.0mm.

3. Door is positioned with its face pressed toward cavity

face plate.

4. Check for microwave leakage around door with an

approved microwave survey meter. (Refer to Micro-

wave Measurement Procedure.)

Note: The door on a microwave oven is designed to act

as an electronic seal preventing the leakage of

microwave energy from oven cavity during cook

cycle. This function does not require that door be

air-tight, moisture (condensation)-tight or light-

Upper Oven

Hinge

Upper 

Oven

Hinge

Lower 

Oven

Hinge

Lower 

Oven

Hinge

Choke Cover

Door

Panel

tight. Therefore, occasional appearance of mois-

ture, light or sensing of gentle warm air movement

around oven door is not abnormal and do not in

themselves indicate a leakage of microwave en-

ergy from oven cavity.

Figure C-6. Door Replacement

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Sharp R-770B Service Manual Page 28

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