I am helping someone run a suite of carbonate samples. We started up the Delta which had been on but pumped down but not running for two weeks. We ran a sequence of standards which looked great.  We then ran several standards before her samples. On the second sample the trace dropped to nothing but noise. There is emissin but the HV hovers around .56.

The filament is not very  and shows a resistance of .15.   I can find no shorts anywhere, and examination of the source did not show any issues with the source or filament.

Before I get in too deep does anyone have any ideas?

Thank you very much.
Stan Klonowski