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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, A191BD only)
There
is no oil in between the condenser
top lens and slide, when using
100X objective
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, A191BD 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, A191BD 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, A191BD only)
Make sure the oil
contact the bottom of the slide and the top of
the condenser during the adjustment.
