Hi there. Operation of a Thermo LCQ Advantage was perfect until turned it to stand-by. Next day, the system was turned on and everything seemed fine. However, TIC signal completely disappeared in the first blank. Came into the LCQ Tune window and yes, the system was reading nothing.
Diagnostics indicated that the Multipole 1 offset was out of control (set at -3 V when actual value as -19 V) as well as Trap DC offset (this latter one scarcely failed, set at -10 V when actual was -10.5). We decided to replace the electron multiplier (the device has 20 years old). Now, Multipole 1 offset is appropriately controlled but Trap DC offset is again scarcely out of range (this has been happening during the las 4 years and we decided not to take it too much seriously).
The problem is that right now, the LCQ is reading ions but masses jump in a 3-4 mass unit range. So, calibration fails since there is no a fixed calibration mass to take as a reference (i.e. MRFA jumps from m/z 522 to 526). Multiplier voltage is nice (-850 V since it is brand new), normal scan fails, zoom scan fails but AGC prescan is OK (but with a high FWHM of 5.5-6). You can also see the typical distribution of calibration masses (caffeine, MRFA and ultramark) but all with wrong masses. We also tried to perform a coarse calibration but the problem is still there, reading of masses is jumping among a 4-6 mass units range. Since we also tune the ring electrode RF and octapole RF voltages, we noticed that the Multipole RF voltage was 2362.5 kHz when it should be in the 2400-2550 range.
We need to know which part of electronics is failing. The biggest and most complex component is the System Control PCB but we would like to be sure that it is the problem before getting a refurbished one.
Of course, Thermo service in Spain said that they couldn´t care about this issue and just said, good luck!!
Many thanks chaps!!
Quique
Just one update.
Restored to factory calibration and tune. All diagnositcs PASSED (lenses/optics, ion detection, power supplies, API voltages, RFs etc.). Right now, the problem is the excessively high FWHR shown by the LCQ that avoids calibration.
Compared to previous calibration reports the situation of FWHR is as follows:
-In normal scan calibration, current FWHR is in the 3-4 range for all calibration masses when it should be around 0.5.
-In AGC scan mass calibration, current FWHR is in the 4-6 range when it should be in the 2-3.5 range.
-Zoom scan calibration turned impossible under current conditions.
In summary, the problem was apparently initiated by some issue related to lenses/ion optics that avoided ions detection. Then, the electron multiplier was changed, Tune and Calibration was restored to factory settings and now the problem is the huge FWHR exhibited by the LCQ (ion detection/sensitivity is OK but mass resolution is lost).
Probabilisticaly, main system PCB (replaced 10 years ago) can be the origin of everything and may have a kind of erratic malfunction (sometimes it works fine and some others no...). Any idea about how to fix FWHR will be very welcomed.
OK, problem solved.
Initial problems about no signal response was solved by replacing the electron multiplier.
Problem appeared concerning excessive high FWHM was solved by retighten the Helium connection and then, ions were appropriately cooled-down and packed returning FWHM to normality. Now calibration is nicey and the system is like brand new.
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