Dear Kim,

We had similar problem with our 602 and the origin was a leak on the
connection between diffusion pumps and the rotary pump.  It has been
impossible to detect with the mass spec itself.  We found the leak by
replacing the rotary pump by a He leak detector.

Bon courage

Christian



____________________________________________
  Christian France-Lanord
  CRPG-CNRS, BP 20, 15 rue Notre Dame des Pauvres
  54501 Vandoeuvre les Nancy, FRANCE

        tel (33) 03 83 59 42 20 bureau / 03 83 59 42 32 lab
        fax (33) 03 83 51 17 98

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