Monika,
I saw a problem like this on a Unity/Inova 500 a while back.
I think you have a bad ADC board. Collect one scan of something like 50:50
h2o/d2o and then display the fid (df). If the time domain data has spikes
in it that is probably from a bad analog-to-digital converter board (an easy
swap). I was once lucky enough to have an old Varian 500 console with four
ADC boards, so when one went bad I just put a new one in the correct spot
(with appropriate dip switch settings) and I was back in business.
I hope this helps.
Good luck,
Jeff
> From: main_at_ammrl.groups.io <main_at_ammrl.groups.io> On Behalf Of Monika Ivancic
> Sent: Friday, March 15, 2024 3:56 PM
> To: main_at_ammrl.groups.io
> Subject: [AMMRL] old Varian HCN probe tuning issues
Hi there spinlanders!
I haven't posted much on this new format that's now existed for almost a year.
I know for a few years old Varian users used an app called Slack, but I'm
wondering if that's no longer being used.
Anyway, our old Varian Unity/Inova 500 doesn't get used often, but we're still
keeping it alive since it's nice to have a 2nd NMR spectrometer in the facility.
During my semester long NMR course I also do 3 labs on this spectrometer, which
I started last week (this week is spring break at UVM). This week I'm starting
to see issues with the tuning. I updated the shims and checked lineshape on
Monday, and that specced out fine AND resulted in giving awesome shims (the student
that used it after the improved shim file got linewidth on the TMS peak at 0.7Hz),
which was on Tuesday. On Wednesday another student used the spec, but he didn't
change the pw to a 90, proceeded to calibrate the 90 pulse (ended up with about a
40 degree pulse) and his T1 inversion recovery experiment consisted of a d1-less
than 90 pulse-d2-less than 45 pulse-acquire. It was at this point that the O1
glitch started becoming more pronounced, whether nt=1 or nt=16.
So today, the O1 (tof) glitch looks pretty bad, here's an image of it with nt=1:
And doesn't go away when ns=16
On Monday I tuned a sample in CDCl3 and found the perfect tuning dip and was able
to center the dip and bring it to the bottom of the screen. Today the dip doesn't
exist, but looks like a wavy form. With a 40Mhz sweep width on Qtune I get the following:
I have not tried to mess with the tune and match knobs, since they were perfect just
on Monday. Did some capacitors/resistors in the probe decide to bite the dust just this week?
Has anyone seen this before?
Please let me know what can be done OR if I need to install a different probe. The 13C
tuning wasn't any better.
Thank you in advance for any insights you might have!
Cheers,
Monika
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Received on Mon Mar 18 2024 - 05:20:06 MST