Opening the NIRC Filter Wheel

The filter wheel has three main parts: They are the ring gear, the cover and the body. Both the ring gear and the body are attached to the cover with 0-80 x 3/16 SS flat head Nylok screws.

  1. Place the wheel on a soft, flat, dust and lint free surface with the screws up.
  2. Loosen the 10 screw that attach the cover plate to the gear about one turn. This to allow for future removal of the body of the wheel while leaving the cover and ring gear attached to each other.
  3. Remove the 5 screws that form the inner ring that holds the cover to the body.
  4. Remove in crisscross fashion the 10 screws that form the middle ring that holds the cover to the body.
  5. Carefully lift off the cover with the ring gear from the body. If the body sticks loosen the cover from the ring gear further.
  6. All of the filter, grisms, etc. are now accessible.
  7. To remove or adjust a grism the 0-80 x ? SS socket head nylok cap screws in the edge of the body must be loosened.
  8. The filters, grisms, etc. can be pushed out from the bottom of there holes. They should only be touched with clean optical tissue.
  9. The best order for inserting filters is filter first, then thin spacing ring, then bronze spring ring, and finally thicker spacing rings with the thickest one last.

Reassembly

  1. Check that the grism adjusting screws are tight if they were loosened.
  2. Put the cover with ring gear back over the body making sure that all the rings are in the wells.
  3. Insert the screws in the holes using new nylok screws if the old ones are worn.
  4. Tighten all screws that hold the cover to the cover incrementally in a crisscross fashion until they are tight.
  5. Tighten the screws that hold the cover to the ring gear in a crisscross pattern. Replace them with new Nylok screws if they are worn.
  6. Check to see if all rings and filters are properly in the well by placing the filter on a flat or using a straight edge to see if the cover is bowed.

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