Pumpdown Safety Shutdown - HP 5973 Hardware Manual

Electronics
8
AC board

Pumpdown safety shutdown

In MSDs with serial numbers XX820XXXXX and above, the ac board will shut
down both the high vacuum and the foreline pump if the system fails to pump
down correctly. The conditions that trigger shutdown are:
• Diffusion pump MSD: foreline pressure above 300 mTorr after 4 minutes
• Turbo pump MSD: turbo pump speed below 80% after 8 minutes
This is usually because of a large air leak: either the sideplate has not sealed cor-
rectly 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 restart the MSD, find and correct the air leak, then switch the power off and on.
Be sure to press on the sideplate when turning on the MSD power to ensure a good
seal.
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