Complete Teardown, Cleaning, and Reassembly of the Olympus BH-2 Coaxial Focus Mechanism Revision 4 Page 10 of 40
arm casting and remove the rear cover to gain access
to the focus gearbox and rack within (see Figure 7).
Figure 7 – Remove the rear cover from the pillar arm
Remove the Focus Gearbox
Lower the sliding focus block to its lowest position using
the coarse-focus knobs, in order to prevent the sliding
focus block from dropping unexpectedly when the focus
gearbox is removed from within the pillar arm casting.
Use a 2.5mm Allen tool or driver to remove the four
M3X10 hex socket-head cap screws and washers
securing the focus gearbox into place in the pillar arm
casting (see Figure 8) and remove the loose focus
gearbox (see Figure 9).
Figure 8 – Remove screws and washers holding gearbox
There should be two brass shims present between the
mounting flanges of the focus gearbox housing and the
pillar arm casting. These shims may be loose, or they
may come out stuck to either the gearbox flanges or
remain stuck to the pillar arm casting (see Figure 9). If
they are not loose, it may be tempting to leave the
shims in place (either on the gearbox housing or to the
pillar arm casting), but you should remove them and
place them someplace safe so that they do not fall out
and get lost at some later point during the repair.
Figure 9 – Remove the loose gearbox and the brass shims
Remove the Focus Rack
Now that the focus gearbox and the two accompanying
brass shims have been removed from the pillar arm
casting, the next step is to remove the brass focus rack
from the back side of the sliding focus block. With the
sliding focus block positioned at its lowest point, use a
2.5mm Allen tool or driver to remove the M3X8 hex
socket-head cap screw securing the top of the brass
focus rack onto the back of the sliding focus block (see
Figure 10).
Figure 10 – Remove the top screw holding the focus rack
Once the top screw has been removed, reach around to
the front of the pillar arm with one hand and raise the
sliding focus block to its uppermost position, such that
the bottom screw securing the brass focus rack can be
accessed for removal. While holding the sliding focus
block in this position, use a 2.5mm Allen tool or driver
to remove the lower M3X8 hex socket-head cap screw
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