Varian 990 dCLD II, Operation Manual

Page: 113 / 162

Model 990 dCLD II Component Leak Detector
5-19
5.5 Ion Source Replacement Outside of
Spectrometer Tube Overhaul
The ion source has 2 filaments. The spare is automatically turned on when Filament 1 burns
out, or by entering the
n INIT-FILAMENT<CR> command (where n is the number of the fila-
ment you want to turn on) or, if the optional front control panel is installed, by manually
touching the filament selector box located on the Manual Tuning screen (Section 4.7.2
“Manual Tuning” on page 4-19). Calibration may be necessary to obtain maximum sensitiv-
ity after changing filaments. It is recommended that the ion source be replaced as soon as
convenient after the spare filament has been put into use. Replacement takes about 3 min-
utes.
Tools: Slotted screwdriver
Parts: Ion Source
1. Turn off the main power switch located on the back of the 990 dCLD II leak detector.
2. Loosen the holding screw to remove the spec tube block connector from the
spectrometer assembly.
3. Remove the cal leak valve block connection and the turbo power connection from the
spec tube block connector.
4. Vent the spectrometer tube by loosening the KF-25 (ISO NW-25) quick clamp and
tipping the spectrometer tube away from the high vacuum system manifold.
5. Remove the 4 slotted screws that secure the ion source header (Figure 5-6 on page 5-9).
6. Remove the ion source header by pressing down on the center post and lifting the
header up and off of the ion source.
7. Gently slide the ion source out of the spectrometer tube body (Figure 5-9 on page 5-11).
NOTE
Dark carbon-like deposits around the ion source filament and/
or a rainbow-like discoloration on the inside walls of the ion
source cavity indicate that the spectrometer tube has been
operated at too high a pressure. This can occur from a system
pressure leak or transferring into test at too high a pressure.
8. Remove the ground slit plate (Figure 5-12 on page 5-12) by placing a thin, straight
screwdriver snug into the slot and carefully twisting and prying with the screwdriver.
9. Examine the ion source (Figure 5-10 on page 5-11) and cavity for deposits and
discoloration. When examination is completed, discard the ion source or return it to
Varian for exchange.
10. Inspect the ground slit plate (Figure 5-17 on page 5-15) and ion source cavity
(Figure 5-11 on page 5-12) to verify that they are clean. If not, follow applicable
instructions in Section 5.3.6 “Examining and Cleaning the Spectrometer Parts” on
page 5-15 to clean the spectrometer body and ground slit plate.