Agilent Technologies 7000 Triple Quadrupole GC/MS, Maintenance Manual

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Electronics
8
Troubleshooting and Maintenance Manual 175
•
Turns on the turbo pump once the foreline pressure is low enough, as
directed by the main board.
• Turns off the turbo pump if the foreline pressure is too high.
• Passes the foreline pressure signal from the foreline gauge or turbo pump
speed and other vacuum status information to the main board.
•
Turns off the foreline pump in case of a problem with pumpdown.
Turbo pump control
Your MS is equipped with a turbo pump with an integrated controller.
The AC board sends control signals to, and receives turbo pump status
information from, the turbo pump controller. The turbo pump controller
provides power to the turbo pump and regulates pump speed.
If the pump fails to reach 80% speed within 10 minutes after beginning
pumpdown or if the speed drops below 50% during operation, the controller
shuts off the turbo pump and the AC board shuts off the foreline pump.
Pumpdown failure shutdown
The AC board will shut down both the high-vacuum and the foreline pump if
the system fails to pump down correctly. One condition that triggers shutdown
is turbo pump speed below 80% after 10 minutes, or if the foreline pressure is
above 300 mTorr after 10 minutes.
This is usually because of a large air leak: either the side plate has not sealed
correctly or the vent valve is still open. This feature helps prevent the foreline
pump from sucking air through the system, which can damage the analyzer
and pump.
To correct the problem, power cycle the MS and troubleshoot. You have
10 minutes to find and correct the air leak before the system shuts down
again. Be sure to press on the side plate when turning on the MS power to
ensure a good seal.