Noise does not increase

If increasing the EM voltage does not increase the amount of noise in the repeat profile scan, the electron multiplier or related electronics are probably malfunctioning. Check the following as possible causes of no peaks:

Bad signal cable connection

1. Remove the upper MSD cover.

2. Check the signal cable. Make sure it is firmly connected to the side board.

Bad detector wiring connection

1. Vent the MSD.

2. Open the vacuum manifold.

3. Check the detector (electron multiplier) wires. Make sure the connections are good. Make sure the wires do not touch any metal surfaces.

See the MSD maintenance documentation for instructions for opening the vacuum manifold.

Failed electron multiplier horn

Replace the electron multiplier horn. See the MSD maintenance documentation for instructions for replacing the electron multiplier horn.