I am experiencing problems with Varian 450-GC hyphenated to 240-MS. I closed the valve for and hour due to septum/liner change, and opened after 1h, and after that, all of a sudden the ion gauge pressure decreased to 3,5 mTorr (previously was always between 9,8-9,6 mTorr), foreline pressure decrease from app.26 mTorr to 14 mTorr and also current and power of the vacuum system decreased slightly.
I injected few etac and there was a strange noise coming from the MS, as far as I could detect. The baseline decrease drastically, and completely changed shape.

I need your opinions about the problem.



Thank you.