Hi Eugenio,
Last time I saw this, the top of the shim stack was dirty. The sample
couldn't rotate so the system didn't recognize the sample as down. It
started intermittently then more frequently until it was about 1/4 of all
samples. So you might try cleaning that first.
One option is the "giant Qtip method" - wrap several large Kimwipes around
an appropriate non-magnetic stick, moisten (not dripping) with IPA or
methanol, then insert down the bore with gentle pressure and swab it. The
wad should press against the sides of the BST but not too snugly. If the
kimwipe comes out dirty, repeat.
If that helps, great. If it sort of helps, you might need to remove the
shims and clean the top out including the little holes. If it doesn't help
at all, that's probably not the issue.
Cheers,
Andrew
On Tue, Dec 16, 2025 at 3:53 PM Eugenio Alvarado via groups.io wrote:
> Dear all,
>
> Recently, our Avance Neo 500 with a SampleCase is having more frequent
> random issues with about 10% of samples that don't seat completely
> inside the magnet. The samples lift and descend properly in the magnet
> but sometimes they just don't settle down properly, even after a delay
> of 30 or 45 seconds, causing IconNMR to eject and try inserting the
> sample several times until it gives up. When that happens, not only
> that sample fails, but also the next one in the queue, probably because
> its start time has timed out after the previous attempts. The gas flow
> pressure in the console is set at 4.5 bar and I just changed the "VT gas
> flow limitation" in the BSMS Web Services interface from 700 to 250 with
> just a little improvement. The VT gas flow in standby is 40 l/h and
> for operation it is 400.
>
> Can anyone please suggest any other parameter to adjust to make sample
> insertions more reliable? Or could it be a problem with a valve?
>
> Thanks in advance,
> Eugenio
>
> --
> Eugenio Alvarado, Ph.D.
> NMR Facility Director
> Chemistry Department, room 3500. University of Michigan
> 930 N. University Ave., Ann Arbor, MI 48109-1055.
> Voice: (734)-764-9924
>
>
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Received on Tue Dec 16 2025 - 15:21:31 MST