If increasing the EM voltage increases the amount of noise in the repeat profile scan, the electron multiplier and related electronics are probably working correctly. Check the following as possible causes of no peaks:
If the calibration vial is empty, you should see the error message: Not enough signal to begin tune or possibly No peaks found. If the vial is almost empty, you may instead see symptoms such as inconsistent peak widths.
Remove the upper MSD cover.
Check the PFTBA level in the calibration vial. If necessary, add PFTBA.
See the MSD maintenance documentation for instructions for refilling the calibration vial.
Excessive pressure can reduce or eliminate the signal. At typical column flow (0.1 to 2.0 ml/minute), foreline pressure should be between 20 and 100 mTorr. Vacuum manifold pressure should be between 1 x 10^-6 and 1.4 x 10^-4 Torr. If pressure is too high, reduce the column flow and/or check for air leaks.
Switch the filament and when prompted to autotune, click YES.
If the MSD passes tune, use this filament. Replace the first filament when convenient.
If the second filament does not pass tune, vent the MSD and check the filament wiring connections.
Check the filaments. Replace them if necessary.
See the MSD maintenance documentation for instructions for replacing a filament.
Initiate an autotune.
Listen for a click when the calibration valve is supposed to operate. If you don't hear the click, either the valve or the electronics controlling it are not working properly. Replace the calibration valve.
See the MSD maintenance documentation for instructions for replacing the calibration valve.
Vent the MSD.
Open the vacuum manifold.
Make sure all wires between the feedthrough board and the ion source are securely connected.
See the MSD maintenance documentation for instructions for opening the vacuum manifold.