50 5977B Series MSD Troubleshooting and Maintenance Manual
2 General Troubleshooting
Foreline pressure is too low
If the pressures you observe are below 20 mTorr, check for the following:
• Column (carrier gas) flow is too low
• Column plugged or crushed by an overtightened nut
• Empty or insufficient carrier gas supply
†
• Bent or pinched carrier gas tubing
†
• Foreline gauge is not working correctly
† These could create a fault condition in the GC that would prevent the GC
from operating.
Analyzer chamber pressure is too low
If the pressures you observe are below 1 × 10
-6
Torr, check for the following:
• Column (carrier gas) flow is too low
• Column plugged or crushed by overtightened nut
• Empty or insufficient carrier gas supply
†
• Bent or pinched carrier gas tubing
†
† These could create a fault condition in the GC that would prevent the GC
from operating.
Gauge controller displays 9.9+9 and then goes blank
This indicates the pressure in the analyzer chamber is above 8 × 10
-3
Torr.
• Solvent peak from an on-column injection
• MSD has not had enough time to pump down
• Excessive foreline pressure
• Vacuum gauge has failed
• Line voltage too low
• Turbo pump is not working correctly
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