Agilent Technologies 7000 Triple Quadrupole GC/MS, Maintenance Manual

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34 Troubleshooting and Maintenance Manual
2
General Troubleshooting
Mass Spectra General Symptoms
This section describes symptoms you might observe in mass spectra. Some of
these symptoms will appear in the mass spectra of samples. Others you will
observe only in a tune report. Some of these symptoms have causes that can be
corrected by the operator. Others, however, require service by an Agilent
Technologies service representative.
Two of the chromatographic symptoms, Poor sensitivity and Poor
repeatability also apply to mass spectra.
No peaks
• Ion source cables not connected
• Bad connections to or from the detector
• HED power supply output cable has failed
• Collision cell voltages
• Collision cell gas flow
• Other electronics failure
• Incorrect tune file (inappropriate parameters)
Isotopes are missing or isotope ratios are incorrect
•
Wrong precursor or wrong product ion was selected
• Scan speed is too high (MRM mode)
• Dwell time is too short (MRM mode)
•
Electron multiplier voltage is too low
• Repeller voltage is too high
• Wrong ions are chosen
•
High background
• Dirty ion source
• Collision cell voltage
•
Collision cell gas flow
• Detector iris not working