R-1900M (serv.man7). Test Procedures - Sharp Home Appliance Service Manual (repair manual). Page 2

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.