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Mass spectrometers / LQT Convectron gauge pressure too high.
I am running an LTQ-Orbitrap XL and have high pressure (2.4 and should be 1) on the convectron gauge for the LTQ. I removed the ion tube to block the ion inlet to the front of the API stack, the vacuum should drop to zero, but only achieves 0.2, therefore I think there must be a leak somewhere between the API stack and the vacuum pumps.
I have tried dripping some methanol around to API stack whilst watching the vacuum levels on the convectron gauge, however I couldn't find anywhere...
If I put my ear to the the panel below the API stack I can hear a small hiss, but I don't know if it is related or not...!
Has anyone had any similar problems or can anyone suggest something to check?
Thanks!