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Date: | Tue, 6 Jun 2000 15:50:28 -0700 |
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All,
I have two questions regarding the mass spectrometers that we have. I'll
give a brief history on the problem and the attempt to solve it.
1) the penning gauge on our VG Optima from one day to the next did not want
to start up. Prior, I shut down the system electronics and the source
controller without switching off the penning gauge. When I started the
system back up the penning gauge did not want to start again (reads 1e+3). I
cleaned the gauge and measured the pins on the cable comming from the
Utility PCB. According to the drawings pins 2 and 7 have to form a closed
circuit to enable the penning gauge. When I switch the penning gauge on on
the computer screen that does not happen. This leads me to believe that the
penning gauge enable circuit on the Utility PCB is not functioning properly.
There is an IC and a Transistor in that circuit that could have gone bad,
however, we cannot find those in the states. The # for the IC5 is SPH610-2
and the TR1 is 2N7000.
Is my assessment correct and if so does anyone know where I could get
replacements for the potentionally bad parts?
2) We also have a VG Prism II which has not been behaving well. On and off
over the last month a Electron volt PCB fault comes up on the screen and
with that the source current is off scale and the filament current is 4.4 in
stead of 3.8. Finally last week the instrument was running fine over the
weekend the source fuse blew (the 5X20 mm, 5A 250V ceramic fuse). I replaced
the fuse and ever since the fault has been coming up again. I also have
taken the source apart 3 times over the last month to make sure that
everything is put back perfectly and I have not been able to find anything
wrong in the source itself. Has anyone had this problem with this instrument
and if so do you have any suggestions where the problem might be?
Thanks very much,
Joost
Joost van Haren
Senior Research Specialist
Columbia University
Biosphere 2 Center
32540 S. Biosphere Rd.
P.O. Box 689
Oracle, AZ 85623
Voice: 520-896-5018
FAX: 520-896-6214
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