Hi Paul,
        I did not write yesterday as I do not have any definitive
solution.  But this might help:

        One time when I installed our 252 source I had lots of
trouble getting it placed correctly.  I struggled with it, in and out
several or many times and ended up with leakage current.  It turned
out that with all the in and out I had coated the quartz tube that
feeds gas to the source with a trail of metal.  I ended up changing
it and it solved the problem.

        One other time I had leakage current and simply removed the
source and reinstalled and the leakage current went away.

        Both of the above times the source was not rebuilt.  Only a
new filament was installed.

Good luck, Jason

>Hmm. No responses.... Does no one have wisdom they can share on 252 leakage
>currents?
>
>Paul
>
>
>At 02:19 PM 05/04/2005, you wrote:
>>Finnigan users:
>>
>>Our 252 source has been giving me a lot of grief in the last week: I have a
>>leakage current in addition to some other difficulties.
>>
>>Two weeks ago the filament was damaged: still functioning but not centered.
>>I replaced it, but opted not to do a full cleaning. It was fine for a few
>>days, but sensitivity started to drop and the leakage current light came on
>>(not immediately).
>>
>>I took the source out a second time, and gave it a full cleaning. No
>>change: poor sensitivity and still a leakage current.
>>
>>I took it out a third time, and swapped out a number of ceramic pieces: all
>>four ceramic posts, and all of the ceramic spacers (some had
>>discoloration). I also paid particular attention to the leads to the
>>feedthrough: none were touching.
>>
>>So, what other causes might there be for a leakage current?  Am I missing
>>anything?
>>
>>In addition to the poor sensitivity, I'm also seeing something completely
>>new to me: a CO2 signal when the change over valve is closed (~10
>>millivolts on mass 44, 45, and 46).
>>
>>- the bellows are empty and pumped out.
>>- vacuum is good (1x10^-8mbar).
>>- seems to be slowly decreasing over time (days).
>>- baking the source has no effect.
>>- background is zero just off peak.
>>- mass scan over the entire range shows the background is only at mass 44,
>>45, and 46. Normal nitrogen traces.
>>
>>Any ideas on either leakage current or the background problem? Might they
>>be related?
>>
>>Paul Eby
>>
>>
>>[log in to unmask]
>>Biogeochemistry Lab (E-Hut, room 102)
>>School of Earth and Ocean Science
>>University of Victoria
>>
>>PO Box 3055
>>Victoria, B.C.
>>Canada
>>V8W 3P6
>>
>>phone: 250-721-6183
>>fax:   250-472-4620
>>
>>
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--
Jason Curtis, Ph.D.
Stable Isotope Mass Spec Lab manager
Associate-In Geochemistry
Department of Geological Sciences
241 Williamson Hall
University of Florida
Gainesville, FL 32611
[log in to unmask], office 352-392-2296
lab 352-392-3344, fax 352-392-9294