R-895M - 13
A
MAGNETRON TEST
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 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.
MICROWAVE OUTPUT POWER
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).
The IEC-60705 procedure must be carried out using laboratory-type procedures and equip-
ment.
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 IEC705
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 1 minute and 36 seconds on full power.
NOTE: The operation time of the microwave oven includes "3" sec. (3 sec. is magnetron filament
heat-up time.)
4. When the 1 minute and 36 seconds 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 90.
NOTE: The result from this test should be within the allowance of 2000cc alternative method.
(
±
10%).
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 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
NEVER TOUCH ANY PART IN THE CIRCUIT WITH YOUR HAND OR AN INSULATED TOOL
WHILE THE OVEN IS IN OPERATION.
PROCEDURE
LETTER
COMPONENT TEST
TEST PROCEDURES
