6-52 | Model 933S UV Analyzer
e. With one hand, grasp the upper portion of the Optical Bench to
support it and, with the other hand, use a 4 mm ball driver to ro-
tate the Lower Cam Pin clockwise and the Upper Cam Pin coun-
ter-clockwise until they are in the “LOOSE” position (see removal/
installation instructions on PMT Cover).
The Cam Pins must stay aligned while the Optical Bench is being
removed from the enclosure. The lined groove on the head of each Cam
Pin must be parallel to the Measuring Cell until the Optical Bench is
removed.
f. Carefully slide the Optical Bench away from the Cell Window
Housing mount. After it is clear from the Cell Window Housing
remove it from the Upper Enclosure.
g. Carefully place the Optical Bench on a static-safe work bench to
work on it.
Use a soft, nonabrasive cloth to gently clean the joining areas (flame-
path) of the Upper Enclosure and its door and make sure the surfaces
are free of debris. Close the door and replace (1) of the M10 screws
while performing maintenance. This will ensure the flamepath is not
inadvertently damaged.
6. Replace the Drive Belt (o-ring) and Bearings (Figure 6-14):
a. Remove the (4) M3 x 8 screws that secure the Chopper Housing to
the Chopper Cover. Separate the two halves of the Chopper As-
sembly.
b. Remove the Drive Belt by rolling it outward and away from the
groove of the Pulley.
c. Remove the Snap Ring and Spring Washer from the Chopper
Shaft.
Remove the Bushings (2), Bearings (2), and Chopper Wheel from
the Chopper Shaft.
d. Replace one Bushing on the Chopper Shaft, followed by a new
Bearing (P/N 300-9437), the Chopper Wheel, another new Bearing
and the other Bushing.
Replace the Spring Washer and the Snap Ring on the Chopper
Shaft.

NOTE
!
CAUTION
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