Re: [AMMRL] Varian NMR lineshape/shimming issue – shoulders and broad components on all peaks

From: Spin-Doc <bert.heise_at_spin-doc.net>
Date: Sat, 15 Aug 2026 10:17:20 +0200
Hi,

I think it is pretty clear from these findings (very misshapen pfg profiles, maxed out z4/z5 shims)
that the probe is vertically misaligned. What kind of repair was that actually?

Fixing that should be fairly easy though - best done with a colleague:
- look inside the black probe case - it should normally contain a small brass hex allen key
- with this you can loosen the one or three (depending on probe type) set screws that fix the probe‘s
outer tube to its mounting bracket. Hold the probe with your other hand to prevent it from sliding down.
- now push the probe upwards until your colleague sees the upper barrel tube (sample delivery tube on top
of the magnet) moving up
- now have your colleague push the upper barrel tube down (you keep
holding the probe but don’t prevent it from adjusting) - until he feels a mechanical end stop
- this should be the correct vertical position -tighten the set screw(s) (hand tight should be enough, don’t apply too much torque)

Now record the PFG profiles again: First reload default shims (observe z4/z5 - are they still near maximum?
If yes, try to load an older shimset from vnmrsys/shims)
The profiles sould hopefully better now?
Anyway I think it‘s a good idea to run 3D gradshim now followed by a Gmap/Z0 autocalibration.

If you have further questions we can maybe take it off the forum to minimize traffic - feel free to send me a direct email…

Cheers
Bert

-> Sent via mobile <-

Spin-Doc 
Magnetic resonance equipment, service, training & more
Dr. rer. nat. Bert Heise
Owner, applications scientist
Kiefernweg 13
58239 Schwerte
Germany
Mail: bert.heise_at_spin-doc.net
Phone: +49-171-5135315

Representing MestreLab software, Stelar relaxometers & Barthel HF amplifiers



Am 14.08.2026 um 21:48 schrieb Uddigiri, Venkateswara Reddy via groups.io <venkateswarareddy.uddigiri=louisville.edu_at_groups.io>:

Hi Bert,
Thank you for your help.
Regarding your suggestions:
• Check whether all shims are set (not only Z shims) and post a screenshot of the "Shims" panel.
I have uploaded the shim profile screenshot.
• The shim cable may not be correctly connected to the shim power supply, or a fuse at the back of the power supply may have blown. You did not specify the console type.
The system is a DD2, and I have uploaded an image of the console and setup.
• Please insert the Dâ‚‚O or Autotest sample, perform an autolock, then go to "Tools → Standard Calibration Exp. â†= ’ Setup Gradient Shimming" and record the trial profiles. Type "ff dss" in the command line and post a screenshot.
I have attached the requested screenshots.
• The NMR probe may have moved (typically downward) relative to the shim tube, which would be visible as a misalignment of the two PFG profiles.
The probe was recently repaired, and unfortunately the previous manager did not mark its original position. I have tried several insertion depths, but I still observe the same broad underlying pattern. Images collected at different probe positions are attached.
• If you see dips in the profiles (especially the lower profile), there may be dirt inside the probe. In that case, remove the probe and clean the sample bore with cotton swabs and isopropyl alcohol.
Do you think it would be worthwhile to test the probe while empty to determine whether any signal might be arising from contamination or dirt inside the probe? I plan to clean the probe next and will report back with the resu= lts.
Thank you again for your assistance.
Best regards,
Venky



Groups.io Links:

You receive all messages sent to this group.

View/Reply Onl= ine (#3694) | Reply to Grou= p | Reply to Sender | Mute This Topic | New Topic
Your Subscription | Contact Group Owner |

_._,_._,_
Received on Sat Aug 15 2026 - 05:43:37 MST

This archive was generated by hypermail 2.4.0 : Sat Aug 15 2026 - 14:28:25 MST