If sample detection was intermittent and has gotten worse, my first guess
would be dirt in the spinner turbine. Can you spin the sample?
If not, this points to dirt having built up.
There is one other odd detail--you have to push the probe up to be able to
eject the sample? When you do this, does the shim coil move up slightly
or is it just the probe? It sounds like the 2 parts of your shim system
may have loosened so that the seal between the upper and lower part may be
leaky.
I don't know what kind of sample changer you have or if it was installed
correctly--can you access the 3 screws on the top of the BST that hold the
two parts of the shim system together?
If you can get to those screws, you might loosen the collar under the magnet
that holds the shim system in place and then try tightening those screws slightly.
The collar at the top of the magnet should be tight so the shim system shouldn't
move around too much. They're long screws so you don't want to tighten
them too much or they'll snap, but if they're loose you can tighten them a bit
to compress the o-rings and make a better seal. You might need to try a
couple of times to get them properly tightened so the sample will spin consistently.
If they are the problem. And then once the sample is inserting and ejecting
properly you can tighten that lower ring a bit again. After that you'll probably
need to do a 3d shim because although things won't move around a whole lot, they
will move around enough to mess up your shims just a bit.
Anyway, that's what I'd look at. If it does turn out to be dirt there
are ways people suggest making a giant swab and cleaning the spinner turbine--
seems to work okay and I can send instructions if needed.
Cheers,Mike
On Wednesday, November 6, 2024 at 09:59:56 AM MST, D'Anciaes Almeida Silva, Igor wrote:
Hi,
I have a Avance III 500 MHz NMR that, since Monday, does not recognize
that a sample in inside the magnet with both autosampler and manual mode.
This issue was intermittent for a couple of months, so I was never able to
pinpoint the exact cause.
In manual mode, even if the sample is not detected, one can run experiments,
and the issue will be that the sample will not eject. To eject, I need to
unscrew the probe just enough to be able to push it up and then the sample
ejects. Did anyone encounter a similar issue before?
Best,
Dr. Igor d'Anciães Almeida SilvaResearch Scientist -
NMR CoreUniversity of Missouri-Columbia32A Chemistry Building
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Received on Wed Nov 06 2024 - 09:13:21 MST