After cleaning, tune still not within limits for high mass

We've had several issues with our 5977B MSD in the past few months. I recently spoke with the Agilent engineer that installed the instrument in January 2019 and he made the recommendation to replace the repeller and extractor lens insulator and clean the other lenses. I cleaned the lenses based on the procedure he had shown me in the past. The method uses a "bar keepers friend" and water slurry to clean the lenses followed by rinsing and sonicating with water multiple times, followed by sonication in methanol. However, I only saw an increase in sensitivity from 0.8 to 1.8 in the high mass 502 and from 21% to 51% for mid mass 219 of PFTBA. The system high vacuum gauge reading is normal and the system looks leak free.


The source has been cleaned 3x over the instruments life. The first was in November 2019 after reasonable, regular use (Agilent engineer used the procedure above). Then, in January 2020 I cleaned the lenses, replaced the ion body insulators, and repeller insulators. When I used the same cleaning procedure I was able to achieve mass ratios after maintenance of ~90% for mass 219 and ~7% for mass 502. We did not run many samples before running into some other problems (possibly 20 samples?). I suspected a small leak and troubleshot for weeks. I was unable to determine the original source of the leak in the end- there were several issues- but it did get resolved. I reached out for assistance and the replacement of the parts above and cleaning the source was recommended. 


In this case, could the source need additional cleaning? Attached are the most recent tunes. 


Thank you for your help.

Parents Reply
  • Yes, I even reloaded the stock tune file and re-checked a few days ago- same result. 


    I recleaned the source yesterday and just ran an atune after bakeout. Everything came back much higher this time ~83% 219, ~6% 502. I suspect  I had build up or something affecting the lenses causing the low ratios for high mass compounds in my original cleaning. 


    Thank you for your help!

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