>Dear list members:
>We have a Micromass Optima with Isochrome continueous flow interface here at
>Iowa State University. Recently we are having a vacuum problem. When CRT7
>valve is closed, the vacuum reading is only 3.6E-6 (normally it is
>about 1E-8 mbar). This happened gradually. If we reopened and then closed the
>valve, we can occasionally get a vacuum of 1E-7mbar. But now we can only get
>3.6E-6mbar no matter the CRT7 valve is closed or not. We changed a new
>copper pad seal, a new knife edge and a new wavy washer, the vacuum is still
>3.6E-6mbar. We degassed ion gauge, the reading is still same. When we
tried to
>degas the ion gauge again, the computer gave us message, it reads "ion gauge
>1 bad calibration data" and no vacuum reading in ion gauge display. I
>rebooted the computer but everytime when I try to turn the ion gauge on, I
>gets the same message. Any suggestions regarding to these two problems will
>be greatly appreciated.

One place that CRT7 valve leaks occasionally occur is through the housing
at the pressure diaphragm.  On our Micromass 903, the pneumatic actuators
had to be removed in order to find the bad spot (I assume your newer mass
spec must be much more intelligently designed than our 903 was...).

Travis Saling
University of Washington (more or less)