HI David--

I like getting helpful hints from other people's questions ;)

Our one DeltaXP likes to run at 0.6/0.4 (1mA emmission), and it's doing 
ok--but I should probably check the alignment better.  In the past it 
did like to autofocus on a setting that would arc when the box and trap 
currents were a bit funky, so we had to force the focusing out of that 
range--and it cleared itself up with the next cleaning (and software 
update).

One other thing to double check--source magnets, make sure they are 
proper aligned (sensitivity drop).

take care
gerry

p.s. Thanks Jim and Rolf for the power supply discussion.



On 3/8/10 5:32 AM, David Psomiadis wrote:
> Dear colleagues,
>
> We have a Delta V Plus connected to a GBII. Six months ago we exchanged our
> filament during regular instrument check-up intralaboratory service. After
> autofocusing the source, we applied the regular tests (diagnostic) and
> everything seemed ok. However, we noticed that the ratio box/trap changed
> from 0.7/0.8 before the filament exchange, to 0.8/0.66 . During the last six
> months, this ratio reached tha value 0.9/0.64, which is the actual ratio as
> we speak. we proceeded to cleaning of the source (clear the dark shades on
> the metal parts and on the aperture according to Thermo manual) and
> autofocus again. As this ratio should be less than 1 according to the
> manufacturers, we would be grateful if there were some ideas of how we can
> lower this ratio to reach the initial value (~0.7/0.8). The stability of the
> measurements is good, however if someone should be critical on the long
> term, he could say that there is a trend for slight instability. Any help
> will be appreciated,
>
> Best regards to all,
>
> David
>
>