OCI BDL800IR, Instruction Manual

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Chapter 8 Maintenance 57
6. Loosen the telescopic rod at the top by inserting a small stiff wire or a small drill into
a hole and rotate counter-clockwise. If you need to replace the silver coated spring
wire, repeat.
7. Remove the old electron gun connectors by sliding them off the screw and install new
ones.
8. To put it back together, fasten the top part first then do the bottom part.
9. During the replacement procedure, avoid bending the silver spring. Make sure the
spring winds loosely around the telescopic rod and its ends (where it is clamped to a
connector) are parallel to it. If a corrective action is necessary, gently bend it at the
respective end to make it parallel.
Proceed to replacing the filament:
10. Disconnect the Wehnelt electrode, which houses the filament fixture and replace it
with a new one. Alignment of the Wehnelt electrode is very important, fasten it firm-
ly to the electron gun body, and yet do not over tighten it.
11. Mount the electron gun back to the optics body.
12. Make sure the electron gun is centered, aligned vertically, and pointing outward with
respect to the optics.
13. Assemble the unit back together in reverse order.
Note, the Wehnelt electrode and filament may be replaced without removing the grids, the
screen and the electron gun, if you are comfortable doing so, with the help of a small vise.
Last step is to evacuate, bake out the system, and form the new filament (see Section
5.8.3).