Date: Mon, 6 Jan 2014 17:07:20 -0500
We are having an intermittent problem (once every few days) with our Varian
Mercury MVX-300 that has now become not-so intermittent (now occurs almost
every time we run a spectrum). The lock level slowly drifts downwards and
then suddenly the lock is lost for a few pulses and then it drifts back.
Pegging the lock level very high, playing with gain/power, rebooting and
power cycling the console, doesn't help the situation. When this happens a
bunch of nasty sinusoidal artifacts appear in the spectrum. Example shown
here..
Any suggestions as to what the problem might be would be appreciated. This
system does have PFG - we turned off the amplifier and removed the PFG cable
from the probe to rule out some sort of current leakage to the probe. It
doesn't seem to be related to the PFG. I have a feeling that when the lock
is lost it is caused by a drift in Z0. For a little time the problem
manifested itself as a drift in Z0, perhaps 20 DAC points, accompanied by a
large shift in lock phase. In the current manifestation the lock phase is
not changing.
All the Best,
John
-- John C. Edwards, Ph.D. Manager, Process and Analytical NMR Services Process NMR Associates, LLC 87A Sand Pit Rd, Danbury, CT 06810, USA Tel: +1 (203) 744-5905 Fax: +1 (203) 743-9297 Cell: +1 (203) 241-0143 Skype: jcepna SkypeIn: +1 (203) 885-7458 Web: http://www.process-nmr.com Blog: http://www.nmrblog.com e-mail: john_at_process-nmr.com This email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to whom they are addressed. If you are not the named addressee you should not disseminate, distribute, retain, or copy this e-mail or any attachments. If you have received this email in error please delete and notify the sender.
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