Thermo Scientific DSQ II, Hardware Manual

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3
Troubleshooting
Sensitivity Symptoms
144 DSQ II Hardware Manual Thermo Scientific
Sensitivity Symptoms
If you observe a drop in instrument sensitivity, you should determine if the sensitivity drop
was sudden or if it occurred gradually. A sudden loss of sensitivity can be the result of
component failure or an unnoticed change in the analytical method. Simple errors, such as a
plugged autosampler syringe or too low sample level in the sample vial, can give the
appearance of instrument failure.
Gradual drops in sensitivity are usually the result of ion source, lens, or prefilter
contamination, and are easily remedied by cleaning the ion volume, lenses, and prefilter.
The electron multiplier influences sensitivity and has a limited lifetime. Eventually it will need
to be replaced. Improper GC maintenance is another cause of diminished sensitivity. It is
important to establish a routine maintenance program for the GC, which is described in the
documentation.
Poor sensitivity or sudden loss in sensitivity.
Possible Solutions
• Check the ion volume and holder for contamination.
• There is a large air leak. Run a leak check as part of an automatic tune or look for m/z 28
as base peak in full scan. See “High Vacuum Symptoms” on page 135 .
• Cable J3 on the analog board is connected to J4. Check the cable and correct if necessary.
• Check the filament to see if it is warped. Replace if necessary.
• Check the position of the ion volume. Position it correctly or reinstall it.
• Cables are incorrectly installed or missing. If some ions are present, make sure entrance
lens is plugged in and make sure cables for P1 and P2 are plugged in correctly on the Low
Pass Filter board.
• Dust has collected in the electron multiplier or on the conversion dynode. Blow clean,
dry gas on the electron multiplier and conversion dynode.
• There is a problem with filament or lens control. See “Filament and Lens Control
Symptoms” on page 130 .
• GC column is not inserted beyond end of transfer line or column is broken off in ion
source. Make sure the column is properly installed.
• Injection port liner is contaminated. Clean or replace the injection port liner.
• Graphite or septa particles have contaminated the injection port. Clean the injection
port.
• The injector or septum is leaking. Replace the septum and perform a leak check on the
GC.