ICP-MS 7800 electron multiplier replacement

As long as you do not see any issues in your measurements, you can keep using the EM, until your new EM has arrived. At some point the Pulse HV will reach ~1800 V and the Analog HV will reach ~ 3300 V (if you are lucky). After that you will have to replace the EM and reset the setting of EM so that you can start from default settings and tune the EM from there. Even if the EM tune fails, you can keep using the EM without EM tune, until your EM has arrived, to prevent any down times. My personal advice is that you order a new EM and keep it ready for the worst case. 

As long as you do not see any issues in your measurements, you can keep using the EM, until your new EM has arrived. At some point the Pulse HV will reach ~1800 V and the Analog HV will reach ~ 3300 V (if you are lucky). After that you will have to replace the EM and reset the setting of EM so that you can start from default settings and tune the EM from there. Even if the EM tune fails, you can keep using the EM without EM tune, until your EM has arrived, to prevent any down times. My personal advice is that you order a new EM and keep it ready for the worst case.