Dear Venky,
could you please try and report back the following:
- check whether all shims are set (not maybe only Z shims?) - please post a
screenshot of the "Shims" panel
- specifically if X/Y shims aren't set but even if they do, please click the
"Read default shims" button on the Shims panel. Any major changes in (XY)
shims?
- the shim cable may not be correctly connected to the shim power supply or
a fuse at the back of it may have blown - you didn't specify what kind of
NMR console exactly you have - Mercury, Inova, VNMRS, 400MR, hence I don't
know which shim power supply you may have.
- please insert the D2O or Autotest sample, Auto Lock it and go to "Tools -
Standard Calibration Exp. - Setup gradient shimming and record the "Trial
profiles" spectra. Type "ff dss" in the command line and post a screenshot.
Might be that the NMR probe got moved (typically downwards) relative to the
shim tube - this would be visible by a misalignment of the two PFG profiles.
If however you see dips in the profiles (especially the second, lower one)
it may be that there is dirt inside the probe. In this case, remove the probe
and clean the inside of the sample hole at the top with cotton swabs and
isopropyl alcohol.
Best regards
Bert
> Am 14.08.2026 um 17:22 schrieb Uddigiri, Venkateswara Reddy via groups.io:
>
> Dear AMMRL community,
> I am looking for some advice regarding a persistent line shape/shimming problem
> on our Varian NMR instrument.
> We first noticed that our proton spectra showed unusual broad components/shoulders
> underneath otherwise sharp resonances. Initially, I suspected a sample-specific
> issue, but the same behaviour is also present with an ethylbenzene in CDCl3 standard.
> A few observations:
> The shoulders/broad components appear on essentially every peak.
> The main peaks themselves can still look relatively sharp, but there is a
> broad underlying component or shoulder.
> I cleaned the inside bore of the magnet and repeated the experiment, but the
> problem remained.
> I also recorded the ethylbenzene/CDCl3 standard without doing any additional
> shimming, and when the spectrum is expanded, the same broadness/shoulder is visible.
> The spectra shown were acquired with the sample not spinning (0 Hz), so this
> does not appear to be caused simply by spinning instability.
> The instrument locks normally, but the line shape remains poor.
> I have attached image showing: ethylbenzene/CDCl3 standard spectrum.
> At this point, I am wondering whether this could be related to higher-order or
> transverse shims, sample positioning, the probe, or another hardware- related
> line shape issue rather than a simple Z1/Z2 adjustment.
> Has anyone seen this type of line shape on a Varian system, where every resonance
> shows a similar shoulder or broad pedestal? I would appreciate any suggestions
> on the best way to diagnose this systematically and which shim terms or hardware
> components would be most useful to check first.
> Thank you very much for your help.
> Best regards,
> Venky.
>
>
> <Shimming problem-700MHz.pdf>
Magnetic resonance equipment, service, training & more
Selling & buying used NMR equipment (all vendors)
Dr. rer. nat. Bert Heise
Owner, Applications Scientist
Spin-Doc Bert Heise
Kiefernweg 13
58239 Schwerte
Germany
Mobile: +49 171 5135315
Email: bert.heise_at_spin-doc.net
Web: http://www.spin-doc.net
Representing:
Stelar Fast Field Cycling NMR Relaxometers (
http://www.stelar.it)
MestreLab NMR Software (
http://www.mestrelab.com)
Barthel HF Amplifiers (
http://www.barthel-hf.de)
-=-=-=-=-=-=-=-=-=-=-=-
Groups.io Links: You receive all messages sent to this group.
View/Reply Online (#3691): https://urldefense.com/v3/__https://ammrl.groups=
.io/g/main/message/3691__;!!PvDODwlR4mBZyAb0!XOABITZnwqyqvm3AZR82vPZ7cDqbu9=
HqrsD2fCyfwr8lyNwfDTt596VA756bCiPSEbHqmtyJspb9pX5OLXXFCQ$
Mute This Topic: https://urldefense.com/v3/__https://groups.io/mt/120751205=
/7559972__;!!PvDODwlR4mBZyAb0!XOABITZnwqyqvm3AZR82vPZ7cDqbu9HqrsD2fCyfwr8ly=
NwfDTt596VA756bCiPSEbHqmtyJspb9pX7Iqda8ig$
Group Owner: main+owner_at_ammrl.groups.io
-=-=-=-=-=-=-=-=-=-=-=-
Received on Fri Aug 14 2026 - 09:37:22 MST