G1946D autotune fail vcap

We recently reactivated an old G1946D with ESI-source which had low signal intensity before shutdown. After Cleaning everything, the signal intensities while autotuning with ESI-mix where better, but while trying to tune vcap it fails at 1700-2000V with the error "no ions found". Using the default settings I get around 32nA CapCurr and 1.6uA ChamCurr. In manual tune mode, ion count (for the 622 m/z ion) drops to noise level at around 1500V. Vacuum seems ok with 1.2-1.5x10-5 torr.

I wonder what would be the best order of (recleaning/ replacing) parts and what would cause this symptom.

With kind regards, Martin

Parents Reply
  • Hi dc1paa,

    at 2000V I get around 25nA CapCurr and 1.2uA ChamCurr and the signal for the 622 m/z ion is quite low (couple thousand cts) but clear and narrow (PW 0.68). Threshold to see a signal in manual tune mode is around 1500-1600V. This should be lower?!?

    The HV has only some milliOhms, so I suspect it to be ok. I already checked all cables going into the vac chamber prior pump down, because they are not accessible when vacuum is applied.

    But thank you for this suggestion anyway, sometimes one overlooks the simple things,

    kind regards, Martin

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