Hello,
I am having problems with our Varian Mercury Plus 200MHz NMR. Students are the primary user of the instrument and they rely on Custom Q to run their spectra. The error message that keeps appearing is "z0 not changed, s/n too low", and then the spectrum will not run. I know that our gradient shim map is up to date and that we have a good current shim file. I also have made sure that the probe has not dropped and that it is securely in contact with the upper barrel. I am able to obtain good quality spectra when I manually lock and shim but for some reason the automation does not work. I tried to calibrate Lock map and z0 with the 4Hz H20/D20 sample and get a new gradient shim map, however, the gradient map generation is always aborted and a message appears saying "gradient map failed, check PFG amplifier and pfgon parameter". I know that for our system pfgon='nny' and that is correct. Also I see on the dg screen that "gradient z out of range, clipped to -2064 or +2064". Agilent has been no help on this matter. Does anybody have an idea what may be wrong. I have never had a problem like this one, nor have I had any problem calibrating lock gmap and Z0.
Thank you,
Dan
Dan Durant
Department of Chemistry and Biochemistry
Mount Allison University
Sackville NB
E4L 1G8
506-364-2699
Received on Wed Mar 02 2011 - 06:25:29 MST