High Electron Multiplier Voltage - HP 5973 MSD Hardware Manual

High electron multiplier voltage

The electron multiplier voltage can range from a few hundred volts to 3000 V. If the
CI autotune program consistently sets the electron multiplier voltage at or near
3000 V, but can still find peaks and complete the tune, it may indicate a problem.
Possible Cause
The filament is worn out. The CI filament may wear out without actually breaking.
Check the Electron Energy ramp; the curve should have a definite maximum with
an inflection point. If the curve is linear with a positive slope and no inflection point,
and the EMV is high, the filament has stretched to the point where it does not line
up with the hole in the ion source body, and most electrons are not getting into the
source.
Action
Replace the filament.
Possible Cause The analyzer is not at the proper operating temperature.
Action
Verify the ion source and quadrupole temperatures. The default source
temperature is 250°C for PCI and 150°C for NCI. The quadrupole temperature is
106°C for both CI modes.
Possible Cause
The CI ion source is dirty.
Action
Clean the ion source. See the Maintenance chapter in this manual for more
information.
Possible Cause The electron multiplier (detector) is failing. Switch to EI mode and confirm.
Action
Replace the electron multiplier.
 Troubleshooting
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