10-155 Filament replacement procedure

Print Friendly, PDF & Email

This blog post is an updated version of the 10-155 filament replacement procedure first published on the RBD Instruments website as a Technical Tip a number of years ago. This version has been updated with some close up pictures of the electron gun assembly shown at the bottom of this post.

Use gloves, de-magnetize all tools and clean all tools with Isopropanol.


  1. Set analyzer on stand or use manuals and support analyzer on handles, facing up.
  2. Remove outer magnetic shield (4 screws)
  3. Remove inner magnetic shield (4 screws)
  4. Carefully remove conical ceramic
  5. Loosen VM (outer cylinder) wire and lift inner cylinder off of base ceramic.
  6. Remove 3 screws inside inner cylinder.
  7. Carefully lift inner cylinder up and off of the electron gun assembly. Note: If the inner cylinder does not move freely, use a heat gun to expand the inner cylinder so that it will slide off. Do not force it!
  8. Look at the 10-155 electron gun detail PDF file to familiarize yourself with the electron gun assembly.
  9. Remove the three long screws that hold the electron gun assembly together.
  10. Remove the V1 emission screw
  11. Remove the 2 filament couplers from the filament posts. You will need a .048 4 spline wrench.
  12. Remove the 3 filament ceramics.
  13. Remove the filament assembly. Note the orientation of the emission tab and filament posts.
  14. Remove the 3 screws that hold the filament base on and remove the filament.
  15. Install the new filament in the same orientation as the old filament into the emission cap.
  16. Install the 3 screws and the filament base and tighten slightly.
  17. Position the filament so that it is centered in the hole and tighten the 3 screws. This is best done using a microscope.
  18. Install the filament assembly on top of the 3 filament ceramics and use the 3 long screws to hold the assembly together. The three long screws need to be tightened so that they all have the same distance with respect to the base.
  19. Reconnect the V1 wire
  20. Reconnect the filament couplers.
  21. Ohm out the connections to the filament and V1.
  22. Degauss the gun assembly.
  23. Install the inner cylinder over the electron gun assembly.
  24. Reinsert and tighten the three screws inside the inner cylinder.
  25. Reinstall the outer cylinder and attach the VM wire.
  26. Carefully install the conical ceramic. The resistor part should be 180 degrees out from the bottom flat ceramic. Ohm out VM to ground and make sure it has the correct resistance – typically that is about 3 Meg ohms from VM (the outer cylinder) to ground. You may need to shim the inner or outer cylinder with some silver or platinum foil, see the 10-155 shim document for more information. Both the flat and conical termination ceramics need to make a good electrical connection in order for the CMA to properly focus the electrons into the analyzer aperture.
  27. Install the inner magnetic shield
  28. Degauss the analyzer.
  29. Install the outer magnetic shield.
  30. Degauss the analyzer. Installation complete!

RBD Instruments provides the C75-010  filament and electron multiplier used in the 10-155 CMA. Contact us for more information by visiting our website at rbdinstruments dot com by clicking on the RBD logo on our blog’s homepage.

This slideshow requires JavaScript.

4 thoughts on “10-155 Filament replacement procedure

    • Hello David,
      Good catch, that was incorrect in the PHI optics post and I have corrected it. Should be about 3.0M to ground on VM.

  1. You guys should make a video of the procedure. That being said keep up the good work.
    Useful procedure to show would be to deposit phosphorus on LEED screen 🙂

Leave a Reply

Your email address will not be published. Required fields are marked *