Stephen,
Some things you can try:
I would try a sample with a solvent with a stronger deuterium signal (d-DMSO,
d-acetone). If you're still having locking troubles, then your deuterium
preamplifier slice may be defective.
Another possibility is that your magnet may have drifted too much for your
current frequency. Check the field value. If it's way off from 0, then
You can lower the operating frequency of your spectrometer (instead of 400.13 MHz,
try 400.00 MHz) and see if you can lock onto your solvent more easily. This
way, you don't have to get the field boosted.
Once you adjust the operating frequency, put your lineshape (1% chloroform
in d-acetone) back in and see if you can lock normally.
The other possibility is that your lock board may be dying. You can check
the signal coming out of the board with an oscilloscope. I'm not sure what
the peak to peak voltage values would be, though.
Ronald Shin
University of Alabama at Birmingham
O'Neal Comprehensive Cancer Center
Central Alabama High Field Nuclear Magnetic Resonance Facility
> From: main_at_ammrl.groups.io On Behalf Of Stephen Nolte via groups.io
> Sent: Tuesday, November 4, 2025 8:18 AM
> To: main <main_at_ammrl.groups.io>
> Subject: [AMMRL] Varian 400MR Lock Failure
Hello,
I've attached the event list of a new error that is trending on our Varian
400MR since late summer. Before the semester started, the reasons for the
error seemed obvious; students were using CHCl3 instead of CDCl3, or there
wasn't enough sample, or the sample was obviously inhomogeneous.
This past week, however, the problem came to a point where no samples could
run, and I couldn't perform a simple proton on my flame sealed ethyl indanone
standard. After some reading, I reset shim values to default, and performed
"su", after which I had no problem running a few samples, and I thought I
was in the clear again.
Yesterday, only three out of ten samples successfully ran a proton, the
seven others all evoked this lock failure error.
Could somebody provide some more guidance?
Thanks!
_______________________________
Stephen Nolte | Chemistry Technician
Millersville University
717-871-7413
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Received on Tue Nov 04 2025 - 07:51:17 MST