For our Delta+, which runs pretty much all day and night about 80% of  
the time, I need to replace a filament about once every 18 months or  
so. A new Thermo-Finnigan filament assembly costs $376, less than a  
dollar per day.

My philosophy on this is that for something as basic (and relatively  
inexpensive) and at the Heart of the Beast, I will go with what I  
know works. Couple that with aging eyesight, clumsy hands, and the  
thought of welding or wrapping  my own filaments just does not compute.

Marilyn Fogel


On Apr 26, 2007, at 2:48 PM, Anthony M. Faiia wrote:

> Jian,
>
> We have been using rebuilt filaments for our Delta+XL and Delta+Ad.
> Initially we rebuilt the filament ourselves by wrapping the wire  
> once slowly around the metal lead. This is a delicate process and  
> quite tedious as the wire will tend to break with such sharp  
> bending. It was good enough for us to use the machine for several  
> years and the intensities were close to a new Thermo filament. We  
> still use this method when necessary.
>
> Lately we have had the filaments rebuilt by Scientific Instrument  
> Services but this last time several were not good. (filaments  
> touching the metal housing, filaments offcenter from the hole).
>
> The wire we use is from Scientific Instrument Services,  1%  
> Thoriated Tungsten wire  with a 0.15mm diameter (the catalog number  
> was W123 but it looks like they don't sell this exact one anymore).
> We tried pure tungsten wire which we were told was the material in  
> the filament but it did not work. Intensities were very low. There  
> were problems with the current regulation on the delta+ad (the box  
> current was too high and the trap current too low). This was with a  
> SIS remanufactured unit. If you send away to have it rebuilt,  
> request that they use 1% thoriated tungsten.
>
>
> Anthony Faiia
> Earth Sciences
> Dartmouth College
>
>
>
> --- You wrote:
> From: Stable Isotope Geochemistry [mailto:[log in to unmask]] On
> Behalf Of Jian Peng
> Sent: Wednesday, April 25, 2007 10:44 PM
> To: [log in to unmask]
> Subject: Re: [ISOGEOCHEM] Filament wire for Delta plus
> [log in to unmask]
>
> Thanks for the replies. They are very helpful. I found out that the
> filament was indeed welded onto the electrodes when I used a  
> magnifier.
> Because of the peculiar structure of the tips of the electrodes it  
> looks
> like that the filament was just pinched in between two thin pieces of
> metal. For this reason I no longer think an amerteur like myself  
> can do
> it. If welding is not a problem I still think it's possible to  
> refurbish
> the filament. The alignment can be adjusted by tweaking the electrode,
> and the tension can be maintained (after welding) by two screws to  
> which
> the electrodes are welded.
> But I understand that there is no easy money to save.
>
> In terms of professional help, I do think it's a good idea to  
> refurbish
> filaments. I haven't done this for Thermo parts, but I have a supplier
> for my two GC-MS systems, he not only supplies exactly the same thing
> (well,
> almost) for a third of the price of the authentic ones, he also offers
> to refurbish the used ones for a quarter of the price ($20) for a new
> one, that is over 90% saving. I haven't done that yet but I have saved
> half a dozen used filaments. I might as well ask them to try the  
> Thermo
> filament for me too.
>
> As for the material of the filament, someone said it's not thoriated
> tungsten, so what is it? Is it made of the same material as a GC-MS
> filament?
>
>
> Thanks a lot,
>
>
> -Jian
> --- end of quote ---