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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.

Regards,

Nabil


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-008 mBar) 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 current. "DEVIATION FROM THESE VALUES INDICATE UPCOMING PROBLEMS CONCERNING THE FILAMENT"
 
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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