Pre-amplifier Replacement (MCT channel)

Tools and Equipment Required

  • Anti-static wrist strap
  • Hex driver set
  • Phillips drivers
  • 1/4″ wrench
  • Replacement pre-amplifier board

Precaution

  • The electronic boards are static sensitive. Always wear an anti-static wrist strap when handling electronic boards.
  • A fragile tri-axial connector is used on the detector connector.  Be sure not to apply any lateral forces when mating and de-mating this connector, to avoid damaging the fragile connector components.
  • Keep the optics compartment clean!
    • Be careful reaching into the interferometer from the top, wear gloves if necessary to prevent contamination of the optics
    • Cover the top of the interferometer box when not actively working inside
    • Look for and clean up any debris that may have fallen into the optics compartment
    • Be attentive to not drop screws and washers in the optics compartment

Procedure

  1. Stop data collection and power OFF the instrument.
  2. Remove the top cover of the interferometer box (16x #4 hex screws, be sure not to loose washers) and store it in a clean location (see Fig. 1). Use all precautions necessary to keep the optics compartment clean, and do not touch any of the optics (mirrors).
  3. Using a 1/4″ wrench, carefully unscrew and de-mate the MCT detector connector from detector dewar (see Fig. 2).  Be sure not to apply any lateral stress to the connector as it can damage the fragile tri-axial connector.
  4. Unscrew the 2x phillips screws holding the MCT ADC case to the MCT preamp case below (see Fig. 2).
  5. Carefully de-mate the ADC case from the preamp case below.
  6. Unscrew the 2x #10 hex screws holding the preamp case to the interferometer breadboard (see Fig. 3).
  7. Remove the preamp case.  Note the path and orientation of the wires surrounding the case, so that they can be replaced in the same position.
  8. Cover / protect the interferometer compartment while the preamp board is being replaced.
  9. Replace the MCT preamp board (see Fig. 4).
    1. Take all precautions necessary to avoid static discharges when handling the preamp board:  always wear and anit-static wrist strap, use an ESD mat if possible, and keep circuit boards in an anti-static bag when not in use.
    2. Open to top of the preamp case to reveal the board inside.
    3. Remove the old preamp board.
    4. Install the new preamp board.
    5. Carefully route the detector connector cable through the opening in the case.
    6. Replace the top of the preamp case.
  10. Replace the preamp case onto the interferometer breadboard using the 2x #10 hex screws.
  11. Re-mate the ADC case to the preamp case.
  12. Secure the ADC with the 2x phillips screws.
  13. Extremely carefully, re-mate the MCT detector connector to the detector dewar.  Be sure not to apply any lateral stress to the connector as it can damage the fragile tri-axial connector.  Use the 1/4″ wrench to tighten the connector.  This will take some time as there is limited access to the screw.
  14. Be sure the top cover is clean, and replace the top cover of the interferometer box (16x #4 hex screws)
  15. Power ON the instrument and return to operation.

 

Figure 1. Top view of interferometer cover

 

Figure 2. Top view of interferometer aft-optics compartment, showing the ADC (MCT), preamp (MCT) and detector dewar

 

Figure 3. MCT preamp case, showing mounting screws

 

Figure 4. Preamp board