>    We are encountering problems while using a Finnigan MAT 252.  The
> emission LED is not turning on.  The cathode reading and trap emission are
> both hovering around zero, and the emission is reading "1.", which I
> presume is the same as no emission.  The electron energy is 0.8 eV, while
> it is usually around 63 eV.
>    However, the high voltage LED is lighting up. The high voltage is just
> under 8kV, and the trap is at 70.0 eV.  Both of these values are typical.
>
>    We have tried changing the filament and checked the source pins for
> shorts, but the problem persists.
>   Can anyone offer us guidance or suggestions?

Gavin, if I remember well, these symptoms are those that we experienced
on our 252 about a year ago. The reason was a dead condensor on the high
voltage electronic board. Once localised, cheap and easy fix.

- Jerome Chappellaz.