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

  • Hi Martin,

    I would check the springs that are around the ion capillary. Especially check the spring at the fragmenter.

  • Hi Martin,

    can you check the vcap setpoint at 2000 V?

    Can you check the HV cable path from the power supply to the capillary?

    Good luck.

  • Thank you very much for this hint,

    The spring in the front seems to be visually intact. To check the spring in the fragmenter I need to vent the system (which I will do after performing some other tasks). The spring in the back is only accessible by removing the desolvation assy, right? Are there any reference values for the resistence or is it only good or none?

    kind regards

  • 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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