Hi,

I'm trying to re-activate a Varian 500-MS LC-MS system (it has been shut down for over a year!). I'm not a newbie when it comes to GC-MS and have even worked for a while with the early SCIEX API LC-MS machines, but I need some help with this as I simply don't know usual problems and "normal" values for vacuum pressure, pump life or common leakage points. It's a small research project with only few money so I have to avoid calling a service engineer (which seems to get more and more difficult since Agilent took over Varian).

The manuals says roughing/foreline pump vacuum should not exceed 1200 mTorr. During installation (2008) it had 900 mTorr, now it has 1280 mTorr. The front turbo pump also has a too high current. I tried the usual things eg. changing pump oil, checking connections, removing temporarily exhaust filter but the pressure did not change.
When I put a small piece of septum over the spectrometer inlet (where the spray enters) the pressure gets down to 28 mTorr.
One of the pumps makes a "not-so-good noise" when turned on, but later it sounds OK. Maybe it is close to life? How long do the roughing pumps last usually? Is there anything I can do to find the problem source?

Thanks in advance
RP18