Orbitrap low S/N （相当权威）

Dear all,
Our orbitrap has not been working well for a while. The file size for a 130min LC-MS/MS run (1 profile MS+ 5centroid MS/MS) decreased from 500-700 MB to 100-200 MB. I re-measured some samples which used to be very good, now the S/N is quite bad, and the spectrum looks very much more noisy, compared to the old run. The column should be fine, since the chromatograph is beautiful. Calibration and tune are both fine with calimix. Thermo technician tried to clean heated capillary, skimmer, tube lens, change the pump oil, pc inside. But it seems it does not help so much.
Does anyone have any experimence related to our problem? or do you have any idea on how to improve the S/N? any kind of suggestion will be appreciated very much.

Thanks!

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