Chromatography Forum

Greetings, I have an Agilent 5975C MSD (G3174A) which had been idle for over a year in another laboratory, so I do not know its entire working history. It holds vacuum and has appropriate air/water values, I cleaned the EI source so the repeller curve no longer looks like a step pyramid and it autotunes tunes well, the filaments look OK.

While looking through all the possible maintenance steps which the unit may need, I have read suggestions in this forum's archives that the RF coils should rarely need adjusting, although doable after watching a Agilent specialist. The manual says that, with both screws being turned equally, the voltage value should be at a minimum value, with typical readings of 70-100 mV for 100 amu and 500-650 mV for 650 amu.

My values are 44 and 297 mV respectively. Is the goal of the adjustment to 'be at the lowest value' or is it to 'fall between typical printed values?' Should I leave well enough alone, or make adjustments?
Thank you

Hello
Imho, if your autotune complete successfully, and tune evaluation is good you don't need to make any adjustments. Rarely we need to modify value of rf coil on our instr.

The goal is actually the lowest value achievable at each mass setting. Your values are great. It is measuring the reflected voltage through the system and the lower the better. If they get too high it can have trouble achieving good peak shapes in profile mode, and really high values can cause feedback to shorten the life of the RF coils. Sort of like tuning a radio transmitter to lowest standing wave values to prevent burnout and increase performance.

Thanks! If our budget allows, I should have an Agilent tech visit for a quick check/PM for things I missed, as well as update the software from Chemstation 2.00 and XP...