I do not know much of the 252. I run a 253 and the source is the same in both.
Check if the source is properly alligned in the housing.
My personal experience is that sometimes it is hard to get the source in the right position. In that case the beam will not hit the cups.
Dipl.-Geol. Michael Maus
Johannes Gutenberg University
Institute f. Geosciences / Paleontology
Von: Stable Isotope Geochemistry [[log in to unmask]] im Auftrag von Kendra Chritz [[log in to unmask]]
Gesendet: Montag, 8. Dezember 2014 22:05
An: [log in to unmask]
Betreff: [ISOGEOCHEM] MAT 252 focusing struggles
We've had a long and exhausting struggle with our MAT 252. We've been trying to return to normal functionality after a power outage months ago. So far, we've cleaned the source and rebuilt it, replaced some old parts on boards in the source controller, replaced the magnet current controller, tested the D/A converter board (and also the amplifiers and the data logger boards). Everything appears to have normal functionality, but we cannot get a signal higher than 30mV of 44 on cup 2 (we should be getting about 1,500mV at the settings we have). No measured shorts in the source, no leakage current, brand new filament.
We've made many passes at focusing the instrument, but we just can't get the signal up. We've even gone so far as to install a test cable for the high voltage boards and measure readouts directly from the potentiometers on BEF while adjusting them, and they all seem to give the appropriate voltage to the lenses. Voltage is good to box, trap and cathode.
I should also add that many of the pots on BEF are maxed out, which seems strange to me. We can't get through a mass calibration because the voltage is too low.
Ref gas on both conflo and dual inlet peripherals are giving the same results.
Is there something I'm missing? Is there anything else I should check?
Department of Biology
University of Utah
257 South 1400 East, Rm 201
Salt Lake City, UT 84112