Hi Neil,
It sounds like the magnet may have been energized with the wrong polarity.
The symptom you are giving is classic. I believe the Mercury console allows
for reversal of this without having to go back into the magnet.
If you would like, I can have one of our Varian engineers contact you.
Best regards,
Jon
www.mrr.com <blocked::
http://www.mrr.com/>
MR Resources, Inc.
The Leader in NMR Systems, Services and Accessories
160 Authority Drive
Fitchburg, MA 01420
978-345-9011
1-888-4-NMR-HELP
_____
From: Jacobsen, Neil E - (neil) [mailto:neil_at_email.arizona.edu]
Sent: Monday, July 06, 2015 12:50 PM
To: ammrl_at_ammrl.org
Cc: Bao, Kevin - (kbao)
Subject: AMMRL: Negative lock level on Varian Mercury-400
I sent a query a while ago about pumping the vacuum space of a donated
Mercury-400. We are now at field and everything works fine EXCEPT:
The deuterium lock will lock in perfectly with lockphase set to 0 or 360,
but the lock signal is negative. The display goes down rather than up when
it locks. The field is stable and you can do long acquisitions. If I set
the lock phase to 180, it doesn't lock and the lock frequency drifts away
from zero frequency.
The problem is that you can't shim on the lock signal. The shim display
(red thermometer) shows zero lock level because it can't display the
negative lock signal.
I've tried many combinations of rebooting the host computer, restarting the
acquisitons computer, power cycling the console, etc. I considered the
possibility that I'm locked on a 2H sideband, but I get a 1H spectrum
centered in the spectral window normally using the standard parameters and
tof=0, and I can't find any other 2H signal in the complete range of Z0
(-2048 to 2048).
I have to assume that some component in the lock system has gone bad during
the long (4 year) sleep of the console, but I keep wondering (since it's a
Varian) if it might be a software issue. I would appreciate any
suggestions.
Neil
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Received on Tue Jul 07 2015 - 05:06:36 MST