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- 14 -
DARKFIELD PROBLEMS
Problem
Cause
Solution
It’s totally dark in
the viewing field
The light is not on
Turn on the light
(A191BOIL only)
There is no oil in
between the condenser top lens
and slide
Place a drop of oil on the top lens of
condenser and let it contact the underside
of slide
(A191BOIL only)
The built-in iris
diaphragm of 100X objective is not
in proper position
Adjust the iris diaphragm ring on the
objective
The condenser is not in the right
position
Lower or raise the condenser slightly to the
position that the specimen is the brightest.
(A191BOIL only)
Make sure the oil contact
the bottom of the slide and the top of the
condenser during the adjustment.
The illumination is
insufficient or too
bright
The intensity of lamp is too low
Adjust the intensity dial to increase the
brightness
The condenser is not in the right
position
Lower or raise the condenser slightly to the
position that the specimen is the brightest.
(A191BOIL only)
Make sure the oil contact
the bottom of the slide and the top of the
condenser during the adjustment.
The condenser is not centered
properly
Adjust the translational centering screws to
center the condenser
(A191BOIL only)
The built-in iris
diaphragm of 100X objective is not
in proper position
Turn the iris diaphragm ring on the
objective
Image of the
specimen is not
clear and lacking in
sufficient contrast
The specimen is not suitable for
darkfield observation
Change to brightfield or phase contrast
(A191BOIL only)
The built-in iris
diaphragm of 100X objective is not
in proper position
Turn the iris diaphragm ring on the
objective
The condenser is not in the right
position
Lower or raise the condenser slightly to the
position that the specimen is the brightest.
(A191BOIL only)
Make sure the oil contact
the bottom of the slide and the top of the
condenser during the adjustment.
