Thermo Finnigan LCQ Deca XP Plus, Hardware Manual

Page: 130 / 216

Service Maintenance
Replacing the Electron Multiplier ________________________________________________
5-24
___________________ LCQ Deca XP Plus Hardware Manual ________________
To replace the anode and cathode of the electron multiplier, or the entire
electron multiplier assembly, proceed as follows:
1. Shut down and vent the system as described in the topic Shutting Down
the System Completely in the System Shutdown, Startup, and Reset
chapter.
2. Remove the top cover of the MS detector as described in the topic
Removing the Top Cover of the MS Detector on page 5-6.
3. Remove the top cover plate of the vacuum manifold as described in the
topic Removing the Top Cover Plate of the Vacuum Manifold on
page 5-6.
4. With an Allen wrench, remove the two socket-head screws that hold the
electron multiplier support to the top cover plate of the vacuum manifold.
5. With one hand hold the high voltage tube and with the other hand hold the
electron multiplier support. Then, detach the high voltage tube from the
high voltage feedthrough in the top cover plate and remove the electron
multiplier as a unit. (The anode remains in the anode feedthrough in the
top cover plate.) See Figure 5-10.
6. Remove the anode from the anode feedthrough by unscrewing it
counterclockwise by hand.
7. Install a new anode (P/N 96000-20076) in the anode feedthrough in the
top cover plate by screwing it clockwise by hand.
If you want to replace the entire electron multiplier, install a new electron
multiplier (P/N 96000-60036) in the next step. If you want to replace only the
cathode, install the old electron multiplier in the next step.
Note. Wear clean, lint-free, nylon or cotton gloves when you handle the
electron multiplier components.
Caution. Be careful not to damage the surface of the electron multiplier
shield. The electron multiplier shield has been electropolished to prevent
field emission.