Hello Million,

In case you haven't solved the problem yet, here are my 2 cents:
We had the exact same "problem" on our Delta Plus XP. The Box current is
0.9mA as well. I tried my best to re-position the filament to no avail. I
ohmed the resistance across several filament we had in the lab. and some of
them had lower readings than others suggesting a variability in
manufacturing. So, I checked the source linearity for Carbon and the values
of our working standards and they were all ok. I asked the Thermo engineer
who was installing our DeltaV XP  and her comment was that this is an
indication that the filament might bite the dust soon since it is drawing
more current than the optimal value. So, I decided to live with it until the
next scheduled source maintenance, barring an earlier emergency repair.

I would suggest that you check the water background and evaluate the source
linearity and precision. If all is ok, then you might want to go with what
you have.



On Dec 27, 2007 9:59 AM, [log in to unmask] <[log in to unmask]> wrote:

> Every one Happy New Year,
> We are having a problem with our Delta plus mass spec for the last two
> weeks. I posted this question 10 days ago. Let me put this in detail if
> someone has some helpful suggestions.
>    1. Two weeks ago Box and Trap current went down from 0.8 and 0.7 to
>    0.6 and 0.9 mA, and after a day the values went to zero. We found
>    out the filament was burned.
>    2. I changed a new filament yesterday and Vac was good (3.3e-008mBar) all the other settings are fine. High Voltage is
>    2.949 KV; Magnet 11591; HV 3.02 KV. When I turned on the source; Box
>    and Trap current readings are 0.9 and 0.62 mA. It stayed the same;
>    it seems to me still there is something wrong. According to the thermo
>    manual the ratio of the "box current" and "trap current" should be
>    0.7 on box versus 0.7 on trap or further in favor for the trap
> I checked all the rotary pumps, all are pumping fine, we removed one of
> the small turbo pumps on the left side of the mass spec it is spinning fine.
> I DON'T know what else to think or try
> Anyone have any suggestions or comments on these problems. Anyone
> encountered this before. I will appreciate the help
> Thanks
> Million
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