Varian NHS-35, Instruction Manual, Page: 42 / 49

Maintenance
3-4
3-5 DISASSEMBLING AND REASSEMBLING THE JET ASSEMBLY
1 To disassemble the jet assembly:
a Disassemble the cold cap water line feedthrough compression seals by removing the
nut, follower, gasket, and female coupling located at the side of the pump.
b Remove the nut which secures the cold cap to the jet assembly.
c Lift out the cold cap.
d Unscrew the hex nut above the top cap and remove it.
e Lift the jet assembly out with a chain fall attached to the cross member now visible in
the jet.
f Once the jet is out of the pump, unscrew the two nuts on the cross member to release
the lower jet stages.
g Disassemble and clean as required.
2. To assemble the jet assembly:
a Reverse the steps outlined above.
b When the jet is installed in the pump body, it is very important that the slot in the jet
base is engaged in the locating pin in the boiler. Unless this is done, the pump will not
function properly.
3-6 HEATER REPLACEMENT
a Determine which heater element has failed at the junction box, then disconnect the two
corresponding leads from the terminal strip. Pull the leads out of the terminal box then out
the elbow cover plate.
b Remove the heater cover and insulation from the bottom of the diffusion pump.
c Remove the nuts holding the clamping plate.
d Lower the entire heating unit (heater element, clamping plate and heater shield, see
Figure 3-2) until it is off the mounting studs.
WARNING
_____________
High voltages (up to 480V) can kill. Always break the primary circuit to
the power supply before starting to work on the heater and/or its wiring.
CAUTION
________
Poor clamping resulting in inadequate thermal contact may result in
reduced heater life and poor pump performance. Tighten nuts finger-
tight on clamping plate, then gradually and evenly tighten them to 250
in-pounds.