Problem
Possible Cause
Solution
�
External connection leak
�
Check and tighten all external tubing
connections; check tubing for cracks;
tighten connections in PTFE heads
�
Gas Ballast is On
�
Switch Gas Ballast to OFF position
�
Vacuum Control is not Closed
�
Closed Vacuum control (CW)
�
Jar “Intake Side” is not tightened in place
�
Use Rubber Wrench to tighten jar
�
Check vacuum pump pressure with external
vac. gauge, attached to pump inlet fitting
�
If external vac. gauge pressure is the
same as unit's display, problem is with
faulty pump or external connection leaks
(mechanical problems)
�
Solenoid valve is not operating properly
�
Valve is always in closed position except
purge cycle. Remove valve silencer and
plug valve inlet with rubber stopper. If
pressure drops it indicates leaky valve.
Insuffic
ient Vacuum
�
Internal leak
�
Bad valve or bad diaphragm; both bad
parts also effect noise; if there is no
vacuum, intake stage is problem.
�
Vacuum level around 30-40 Torr
indicates bad exh. stage, valve or
diaphragm.
�
Bad valve or diaphragm
�
Change Valve / Diaphragm
�
Loose eccentric or counterweight
�
Tighten Loose Parts. Use Loctite
�
Broken diaphragm threaded insert
�
Change Diaphragm
�
Bad Con-Rod bearing or motor bearing
�
Change Con-Rod
�
Broken motor shaft
�
Change Shaft
�
Loose housing cover
�
Tighten housing screws on back of unit
Slide rail loose, remove housing cover
and slightly crimp slide rails on inner top
of housing cover. Do not over crimp.
�
Loose inlet/outlet jars
�
Tighten jars
High
noise
�
Damaged diaphragm
�
Check vacuum performance - See Poor
Vacuum section below
If vacuum is still poor, contact
Welch Technical Support*.
�
Loose motor mounting screws
�
Tighten screws
Exces
sive
vibra
tion
�
Incorrectly installed counterweight or wrong
C'weight
�
Failures described above also contribute to
excessive noise
�
Adjust/reinstall/change C’weight
�
Indicates partially plugged passage, usually
in exh. stage
�
Clean/Unplug Stage
M
ec
ha
ni
ca
l F
ai
lu
re
s
Slow
pump
-down
�
Plugged silencer
�
Unplug /change silencer
18
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