start LC-MS-MS 6420?

Achem , assuming the system was vented and all of the connections are still intact (Rough pump connection, Line voltage to MS, nitrogen for source, nitrogen for CC, etc.) you should be able to power on the system via the front power switch to start up the system. If the items mentioned above are not done properly, your system may vent following start up or simply not turn on. 

Achem , assuming the system was vented and all of the connections are still intact (Rough pump connection, Line voltage to MS, nitrogen for source, nitrogen for CC, etc.) you should be able to power on the system via the front power switch to start up the system. If the items mentioned above are not done properly, your system may vent following start up or simply not turn on. 

Thank you mipastor!

Have you been able to pump down?

Yes , thanks, looks normal