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Pull out the power plug, take off the cabinet, discharge the
capacitor, measure the resistance value of the primary
winding and the secondary winding of the transformer with an
avometer (FIG.5 – 10 and FIG.5 - 9). The resistance value of
the primary winding should be about 2.2 ohms, the secondary
winding should be about 130 ohms. Otherwise, it indicates the
transformer has broken, and should be replaced by a new
one.
If the transformer is normal, then the high voltage capacitor
should be checked. Pull out the connecting plug of the
capacitor, and measure it with R×1 grade of an avometer, the
two rods of the avometer connect the two polarity of the
capacitor. When they just connected, the reading of the
avometer should be zero, then increases to nine megaohm
slowly. Change the rod to different polarity, the reading repeat
from zero to nine megaohm (FIG.5 - 11), it means the
capacitor is normal. If the indicator of the avometer can't point
out from zero to nine megaohms, it indicates the high voltage
capacitor has broken, and should be replaced by a new one.
If it is normal between the two pole of the capacitor, then the
insulation between the capacitor pole and the cabinet should
be measured with R×10K grade of an avometer. The
resistance value should be "∞" (FIG.5 - 12). If it is short
circuited or have a number reading, it indicates that the
capacitor has been punctured or electricity leaked, and should
be replaced by a same model, same capacity one.
Fig.5-10
If the resistance value of the capacitor's two pole are "∞", the capacitor is normal. Then check the earth of the
magnetron's two filaments to see whether they are short –
circuited (FIG.5 - 13). If they are short – circuited and the
filament strikes the shell of the magnetron, it indicates the
magnetron has broken, and should be replaced by a new,
same model one.
If the magnetron is also normal, then test the pilot switch.
Pull out the two plugs of the switch. Measure it with the R×1
grade of avometer, the two rod connect the plug of the
switch, the resistance value should be "∞" (FIG.5 - 8).
Then press down the pilot switch with a screwdriver, if the
reading of the avometer pointed to zero, it indicates the pilot
switch has broken, and should replace it with a new, same
model one.
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Fig.5-11
20
Fig.5-8
Fig.5-9
Fig.5-12
magnetron
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