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Hello again to everyone. My problem with the 20/20 beam focus is solved
(knock on wood).

Just for those who are interested, here is what the problem was:

We had changed the filament three days ago and were able to get the 20/20
back up just fine. The next day I was leak checking our system and the
20/20 showed no apparent problems. Yesterday I noticed that our background
signal (N2) had dropped dramatically from the previous day and then saw
that the beam focus was only at 30% while it was set to 87%.
With some helpful advice from several of you I was able to determine that
the problem was indeed coming from the source and not the electronics.
Opening the source revealed that one of the ceramic insulators on lead 4
(one of the focus plate leads) had slipped down about 2mm from the focus
plate so that it was flush with the source block. Apparently, whenever the
voltage applied to the focus plate exceed about 1200V it would arc to the
source block.
The solution was simply to push the insulator back up to the focus plate
and bend the wire lead beneath the insulator so as to prevent it from
moving again.

Thanks to all of you for your help! If you would like to see the advice I
was given to determine if the problem was with the source or the
electronics just let me know and I will forward it to you.

Anthony Michaud

B40 Savage Hall
Dept. of Nutritional Sciences
Cornell University
Ithaca, NY 14853





>Hello all. I'm using a Europa 20/20 and am having problems with the beam
>focus. Here is a description of the problem:
>
>- In all of the following situations the beam focus was set to 87%.
>
>When the HT is set to 4000V, the beam focus goes to 30%.
>When the HT is set to 3000V, the beam focus goes to 54%.
>When the HT is set to 2000V, the beam focus goes to 65-67%.
>When the HT is set to 1000V, the beam focus goes to 86%.
>When the HT is set to 0V, the beam focus goes to 50%.
>
>I am hoping that somebody out there has had this problem before and knows
>of a quick fix so that I don't have to wait until tomorrow to get help from
>tech support.
>
>Thanks!
>
>Anthony