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)