Varian NHS-35, Instruction Manual, Page: 46 / 49

Troubleshooting
4-2
Table 4-1
Fault Probable Cause Corrective Action
Poor system pressure Leaks in system, virtual or real Locate and repair.
High process gas load Measure gas load, eliminate
cause.
System dirty Clean system to reduce
outgassing.
Poor ultimate pressure Contaminated pump fluid Examine and replace.
Low heat input Check voltage. Check for conti-
nuity, burned-out element, poor
thermal contact.
Inadequate cooling water flow Check water pressure. Check
tubing for obstructions and
backpressure.
Excessive or too cold cooling water Check temperature. Adjust
flow.
High forepressure Check for leak in foreline, poor
mechanical pump performance,
breakdown of mechanical
pump fluid.
Water in quick-cool coil Check and remove cause.
Low heat input Check heaters.
Low fluid level Add fluid.
Malfunctioning pump assembly. Check and repair or replace.
Improperly located jets. Damaged
jet system.
Inlet pressure surges Incorrect heater input Check and correct.
Fluid outgassing Condition fluid by operating the
pump for a few hours.
Leak in system ahead of pump inlet Check and correct.
High chamber Forepressure too high Check for leak in foreline, poor
contamination mechanical pump performance,
breakdown of pump fluid, and
incorrect valve operation.
Prolonged operation at high through- Review procedures.
put at pressure above 10
-3
Torr
Improper system operation and Review procedures.
air release procedures
Pump will not start Safety circuits and/or protective Check utilities, flow switches,
devices prevent contactor from interlocks. Check thermostat
staying closed operation.
Low speed (prolonged-
cycle after checking
gas load conditions)