Televac AN 3004: Cleaning the 7FC and 7FCS Cold Cathode Passive Gauges


This document explains the process for cleaning the Televac 7FC cold cathode and 7FCS cold cathode vacuum sensors that have
been used in harsh environments or operated for extended periods in the 10-4 Torr or higher range.

Materials Needed

The following materials are needed to properly clean the 7FC cold cathode and 7FCS cold cathode vacuum sensors:

  1. 3/16” Allen Wrench


  1. Remove the sensor from the vacuum chamber.
  2. Unscrew the bolts to expose the anode assembly.
  3. Gently lift the anode assembly upwards to separate it from the body.
  4. Remove the copper gasket from the sensor.
  5. Check the knife-edge on both the anode and the body to make sure they are in good condition.
  6. Gently remove any contaminants from the anode using the scouring pad. For the 7FCS, be careful not to damage the starting aid.
  7.  Blast the body with glass beads.
  8. After cleaning, blow out any residual glass beads or dust with dry nitrogen.
  9. Install a new copper gasket in body.
  10.  Replace the anode assembly in the body.
  11. Tighten bolts gradually moving from bolt to bolt to ensure uniform compression of the gasket.
  12. Reinstall in the vacuum chamber.
  13. Allow several hours for tube to degas when pumped down to high vacuum.
  14. If properly cleaned and assembled, the gauge tube is ready for use without re-calibration unless NIST
    traceable calibration is required.