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R-757M - 10
B
HIGH VOLTAGE TRANSFORMER TEST
WARNING:
High voltage and large currents are present at the secondary winding and
filament winding of the high voltage transformer. It is very dangerous to work
near this part when the oven is on. NEVER make any voltage measurements
of the high-voltage circuits, including the magnetron filament.
filament winding of the high voltage transformer. It is very dangerous to work
near this part when the oven is on. NEVER make any voltage measurements
of the high-voltage circuits, including the magnetron filament.
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.
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.
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 carry out this procedure can be found in the Sharp Technical Training notes which is available from
Sharp Parts Centre (part number SERV-LITMW01).
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).
The IEC60705 procedure must be carried out using laboratory-type procedures and equipment.
These requirements make the procedure unsuitable for routine performance checks.
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.
test method must be used.
Alternative simplified method:
1. Place 2 litres of cold water (between 12
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 40 seconds on full power.
4. When the 1 minute and 40 seconds 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 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
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.
investigated.
It is essential that only leakage detectors with current calibration traceable to National Physical
Laboratories are used.
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.
WHILE THE OVEN IS IN OPERATION.
TEST PROCEDURES
PROCEDURE
LETTER
COMPONENT TEST
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