We have a 5975 MSD that is failing to pump down. The turbo pump (Pfeiffer HiPace 300) does not appear to be spinning up, though the turbo pump electronic drive unit has power and is displaying LED light activity. The rough pump has been serviced recently and should be drawing a proper vacuum. All MS cooling fans appear to be functioning properly. The screen on the MS indicates that the pump down has been initiated after powering on the system. ChemStation is giving no error message that would explain why the system is failing to pump down.