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filament terminals, the meter should show a reading of less than 1 ohm.
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.
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.
must be used.
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 temperature as T2.
5. Calculate the output power using the following formula:
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 OVEN IS IN OPERATION.
using an ohmmeter set to its highest range. Connect the ohmmeter across the terminal B+C of the high
voltage rectifier and note the reading obtained. Reverse the meter leads and note this second reading.
The normal resistance is infinite in one direction and more than 100 kΩ in the other direction.
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 windings. The following readings should be obtained:-
should be replaced.
the oven is on. NEVER make any voltage measurements of the high-voltage
circuits, including the magnetron filament.
ohmmeter set to its highest range across the terminals A+B of the asymmetric rectifier and note the
reading obtained. Reverse the meter leads and note this second reading. If an open circuit is indicated
in both direction then the asymmetric rectifier is good. If an asymmetric rectifier is shorted in either
direction, then the asymmetric rectifier is probably faulty and must be replaced with high voltage rectifier.
When the asymmetric rectifier is defective, check whether magnetron, high voltage rectifier, high voltage
wire or filament winding of the power transformer is shorted.
BECAUSE OTHERWISE AN INFINITE RESISTANCE MIGHT BE SHOWN IN BOTH
B. Continuity check must be carried out with measuring instrument which is set to the highest resistance
E. An open capacitor constantly shows a resistance about 10 MΩ because of its internal 10MΩ
G. The resistance across all the terminals and the chassis must be infinite when the capacitor is normal.
If incorrect reading are obtained, the high voltage capacitor must be replaced.
S.C.; Short, O.C.; Open circuit
continuity test across the two terminals as described in the below.
resistance between the two terminals as described in the table below.
Using an ohmmeter, check between the ter-
minals as described in the following table.
An open circuit thermal cut-out (MG) TC2 indicates that the magnetron has overheated, this may be due
to resistricted ventilation, cooling fan failure.
An open circuit thermal cut-out (OVEN) TC1 indicates that the oven cavity has overheated, this may be
due to no load operation.
R2: 680k ohm ± 20%