Extrel Max300-LG - Electron Multiplier Removal and Replacement

Max300-LG : Description - Specifications - Installation Guide
Extrel Core Mass Spectrometers
Page 30
The RF connection flange assembly should then be installed onto the vacuum chamber
with a new 3-3/8" copper gasket. The spring loaded contacts of the RF connection flange
must make contact with the quadrupole rods, not the collar shield end plate or chamber.
The vacuum feedthroughs on this flange, when properly installed, are offset toward the
detector end of the chamber. Initially leave these screws finger tight.
Use the ohmmeter to check the continuity between the feedthrough contacts on the flange
and the quadrupole rods and check for shorts to the chamber. Either the ionizer or the
detector flange will have to be removed to accomplish this. Once verified that the
electrical connections are correct, finish tightening the RF flange screws. The securing
socket head screws (1/4" hex key) should be tightened in a crossing pattern that keeps the
flanges parallel to each other.
If the ionizer mounting flange was removed, it should be re-installed using a new 4-1/2"
copper gasket. The securing socket head screws will require a 1/4" hex wrench. Use the
ohmmeter to check that the ionizer lenses are isolated from one another, the vacuum
chamber and the quadrupole. If the detector mounting flange was removed, it will need to
be re-attached using a new 4-1/2" copper gasket and the 1/4" hex key for the securing
socket head screws. Position the detector mounting flange so that the HV feedthrough is
towards the back of the vacuum chamber. Use the ohmmeter to check that the detector
connection feedthrough(s) are isolated from both the vacuum chamber and the
quadrupole rods.
Electron Multiplier Removal and Replacement
Instruments equipped with the optional electron multiplier detector will require
replacement of this component after the required gain can no longer be achieved. When
this occurs, the vacuum system will need to be vented as described at the beginning of
this chapter before beginning the replacement procedure.
Required Tools:
(1) 1/4" Hex Key
(1) 3/32" Hex Key (Note: a “ball end” type is most convienent.)
(1) 4-1/2" Copper Gasket
(1) Pair Lint Free or Nylon Gloves
(1) #2 Phillips Screwdriver