Hi Dave

I am not familiar with the Prism but initial thoughts would be a 
water flow or pressure switch (if there is one) sticking or a thermal 
switch on the side of a diffusion pump requiring to be reset. 
Otherwise there may be a problem with the Pirani trip relay in the 
vacuum protect unit.

Regards

John

At 12:41 12/10/2006, you wrote:
>We recently moved our '89 vintage PRISM and cannot get high vacuum 
>back again.  The analyser has pumped out normally to 1e-3 mbar but 
>the diff pumps just will not trip back on. Everything seems 'normal' 
>ie all power supplies on, fuse by the rocker switch is OK etc etc. 
>Has anyone experienced this, or know of potential problem areas 
>(sticking relays, faulty switches etc) before I am forced to dust 
>off the schematics?
>
>Thanks for  any help!
>
>dave
>
>
>
>-----------
>Dave Mattey BA PhD FRAS
>Professor of Stable Isotope Geochemistry,
>Department of Geology,
>Royal Holloway College,
>University of London,
>Egham Hill,
>Egham,
>Surrey,
>TW20 0EX
>
>Telephone
>
>01784   443587 (direct line)
>         443582 (dept secretary)
>07780   697564 (mobile)
>
>

John Hill
Mass Spectrometry Facility
University College London
Chemistry Department
20 Gordon St.
London
WC1H 0AJ

Tel:  020 7679 4605
Fax: 020 7679 7451