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Hi Bill,
 
I had a similar problem with a Delta-XL.  By changing the scan setting the
problem went away.  Access the scan settings within the "gas configuration
editor" by right-clicking on the N2 row then select the only menu option,
"Scan Basics".  Next, expand the HV menu then equally decrease the "start
step" value and increase the "stop step" value.  You can also reduce the
"step" size and input a delay to allow for hysteresis.
 
Mark Haught
 

  _____  

From: Stable Isotope Geochemistry [mailto:[log in to unmask]] On Behalf
Of William Mark
Sent: Friday, January 25, 2008 8:48 AM
To: [log in to unmask]
Subject: [ISOGEOCHEM] Halted Runs - Not always a good thing.





Hello All 

I have been experiencing and intermittent "event" for a couple of months now
that is getting worse and needs to be resolved - hopefully someone can toss
me a clue before running to the default , filament replacement. 

This "event" has been seen over a couple of different filaments installed
over a 3 month period; when it's running, the sensitivity, stability and
sample analysis have been very good. I have tried re-tuning several times
with very little change in tune settings or the problem. I do daily Mass
Jump testing etc. 

Lately, with the increased frequency of this "event" the spec has had more
stability issues and notable HV peak centre shifting during Mass Jump
testing. 

In a nut-shell; 

We have a Delta Plus running solid C/N EA samples. At some point during the
run (sample 8, or 53 or 111 - anytime) after analysis the CO2 Ref pulse and
jumping back to Nitrogen for the next analysis, I get a "Fatal Script
Error". This is a drag not only for lost analysis time but it leaves the Ref
Valve open all night. 

It seems, once the jump back to nitrogen is complete, the Ref gas is opened
and before it can run the peak centre, the run is halted.  I have noticed at
this time, that not only is the spec blind to the N2 Ref Gas peak but even
the background levels drop to unfamiliar readings, as though it is no longer
even looking in the proper neighbourhood. 

After sitting for a few seconds, to a few minutes, "blip" the proper
backgrounds come up (or the Ref Gas peak, if it is still open). 

I am ready to pull the filament out and try another but I was wondering if
anyone thinks it could be some other "flakey" electronics/ board. It seems
not to be landing where says (or thinks) it is, after the jump to back to
nitrogen. 

Any thoughts would be greatly appreciated. 

Have a good weekend. 

I am off to a cottage with my 2 younger brothers (leaving our families
behind), to drink beer, watch movies and play Guitar Hero. It may not help
but it can't hurt. 















            Bill Mark 


            Isotope Technician 
            Environmental Isotope Lab 
            University of Waterloo 
            Phone (519)-888-4567 Ext 36747 
            FAX (519)-746-7484 
            http://www.uweilab.ca/