Hello...

        We've just blown two filaments in two days on our Finnigan
Delta Plus XL.  The first filament went sometime after running
approximately 100 zooplankton samples on the EA peripheral (of
relatively small, consistent size).  There is some evidence that we
may have had some power fluctuations around this time, and that is
what I originally thought was the most probable cause.  The first
filament was just over a year old.
        We replaced that filament with the only one we had on
hand...one that was in good condition but had been in the instrument
previously (for approx. 6 months).  In the end we had to solder the
Ag leads to increase their strength, but it was successfully
installed.  After reaching good vacuum, the source was turned on, and
we performed a BSCAN.  The results were satisfying, and everything
seemed to be in order.  Sometime during the night, however, the
filament blew again.   There is no evidence that something funky was
happening with the power.   So we're at a loss.
        Has anyone experienced this sort of problem?  Are there any
diagnostic suggestions?  Any info would be greatly appreciated.

Cheers,
Kendra Turk
_________________________
   Kendra Turk
   NASA/Ames Research Center
   Mail Stop 239-4
   Moffett Field, CA  94035
    650-604-1430 (voice mail)
    650-604-6110 (lab)
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