Glen

Sounds to me as if the problem maybe the peripheral interface adapter i.c. (PIA)
in the STE control unit which controls the switch functions of the Optima such
as the source or in the power distribution.  To start to identify where the
problem lies you must first identify if the command to turn on the source
changes.

On the left hand side of the Optima towards the rear of the instrument there is
an electronic circuit board.  On this power distribution board there are a
series of lights for each switch function.  As you switch the source on and off
you will see one of these lights go on and off.  Mark which light this is.

The next time the source turns it'self off and cannot be turned back on check
the light on this board.  If the light is off then the problem is in the STE
unit and is likely to be the PIA.  If the light is on then the problem is likely
to be on the power distribution board.

Cheers

Peter Stow

Glen Martin wrote:

> Dear People:
>
>         We have a rare but intermittent problem with our Mircomass Optima.
> The source head will turn itself off, and cannot be turned on through the
> Optima software without first doing a hardware reset.
>
>         Doing such a reset results in the loss of the running standard gas,
> and the consequent need for rerunning standards again.This only happens one
> to three times a year, but is rather a nuisance, especially when a sample is
> so small that it can't be rerun.
>
>         The shutdown occurs mainly during the time the system is sitting
> idle with standard running gas entering the source. This has occurred with
> tank hydrogen, tank nitrogen, tank carbon dioxide, and tank 3% argon in
> nitrogen. The weather outside, seems to play no role in this perturbation.
>
>         Some of the electronics people have suggested removing the old surge
> protection devices and replacing them, since the instrument is over five
> years old.
>
>         Comments would be appreciated.
>
>         Thank you.
>
> Glen Martin, School of Natural Resource Sciences, Water Science Laboratory
>         University of Nebraska, Lincoln, Nebraska, USA 68583-0844



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