MAX300-RTG : Hardware Manual Hardware Maintenance
66
be 2.50 inches (63.5 cm). If this dimension is more than 2.54 inches (64.67 cm),
lens 2 will short to the quadrupole rods.
Using a new 4-1/2 inch copper gasket, install the ionizer flange onto the vacuum
chamber. A threaded hole on one side of the electrical feedthrough, visible in
Figure 40 below, can be used to hold the copper gasket in place. Install the bolts
on the flange finger tight.
Figure 40: Reinstalling Ionizer Flange
Note: Never reuse a copper gasket. A scratch undetectable to the eye may be
present and result in a vacuum chamber leak.
Use an ohm meter to verify proper installation of the ionizer before tightening the
ionizer flange bolts. The filaments, thermocouple, and heaters will read low
resistance when measured. Check all the pins for shorts to ground (the chamber)
and to each other. Also check for a short between lens 2 and either of the
quadrupole connections on the top of the chamber. If the quadrupole has been
removed for service, postpone this step until it has been reinstalled. Figure 41,
below, depicts the wiring for the ten pin vacuum feedthrough. Table 1, below,
shows the function of each pin.
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