Vpi Valve Closes Too Slowly; Vpi Valve Opens Too Slowly Or Not Completely; Vpi Valve Fails To Open; Closing Causes Large Burst Of Air Into System - Agilent Technologies VPI Series Instruction Manual

3.4.3 VPI Valve Closes Too Slowly

1. Inlet filter to solenoid valve is clogged. Clean or replace filter.
2. Solenoid valve is defective. Replace with a new solenoid valve.
3. There is excess friction between bushing
bushing and guide pin as described in Section 3.2.1 "Piston/Diaphragm Sub-Assembly"
on page 24.
4. The spring is restricted by contamination. Disassemble, clean, or replace.

3.4.4 VPI Valve Opens Too Slowly or Not Completely

1. The orifices are partially blocked. Clean and reassemble.
2. There is excess friction between bushing
and guide pin as described in Section 3.2.1 "Piston/Diaphragm Sub-Assembly".
3. The diaphragm
reassemble.

3.4.5 VPI Valve Fails to Open

1. The solenoid valve has a leak or will not close properly preventing the evacuation of the
chamber over the piston. Check to make sure that electrical power has been restored to
the solenoid valve. If the solenoid valve is energized, leak check. If a leak is found in the
solenoid, replace the solenoid.
2. Foreline between the mechanical pump and VPI valve has a major leak preventing the
evacuation of the chamber over the piston. Isolate and correct the leak.
3. Excess friction between bushing
described in Section 3.2.1 "Piston/Diaphragm Sub-Assembly" on page 24.
4. The nose piece O-ring
improper installation of a dry (ungreased) O-ring. Follow the instructions in
Section 3.2.2 "Nose Piece O-ring Replacement".
5. The diaphragm
reassemble.

3.4.6 Closing Causes Large Burst of Air into System

1. Diaphragm
Diaphragm Sub-Assembly".
2. Diaphragm
as described in Section 3.2.1 "Piston/Diaphragm Sub-Assembly" on page 24.
28
Vacuum Pump Isolation (VPI) Valve
or spring is contaminated. Disassemble, clean or replace, and
and guide pin. Clean and repair bushing as
is stuck to valve seat due to excess heat, contamination or the
or spring is contaminated. Disassemble, clean or replace, and
is damaged. Replace with a new diaphragm, see Section 3.2.1 "Piston/
has become detached from piston
and guide pin. Clean and repair the
and guide pin. Clean and repair the bushing
and sleeve. Inspect and reassemble