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5977A not pumping down correctly

Question asked by gchaplain Champion on Jan 15, 2020
Latest reply on Mar 11, 2020 by gchaplain

Good day,


We have a 5977A that last week was showing turbo pump speeds dropping to 99.7% and then back upto 100%, no nitrogen present.

This week the Mass spec shutdown due to vacuum issue it was:

- restarted, got to 60% slowly and shutdown (we know this is a time out)

-side door pushed too and restarted whilst pushing - still upto 60% then timeout

-ensured vent valve was closed and restarted- still upto 60% then timeout

-Transfer line nut tightened slightly and restarted- still upto 60% then timeout


Any other suggestions would be useful. Also note that the roughing external pump gets quieter as the vacuum gets stronger (so probably not that causing the issue)


Kind Regards