Re: Odd behaviour with ATM equipped probe. (fwd)

From: Markus Hoffmann <mhoffman@brockport.edu>
Date: Mon Jan 04 2010 - 18:17:25 EST

Hi everyone,

In the meantime, I did make progress on the problem with the help of Bruker probe experts. It is indeed the probe. My understanding now is that the fine adjustment is actually some sliding bar. There must be a bad spot on that sliding bar such that we can get signal at some positions but not others. For example, on the silicon signal, the sliding bar winds up at a different portion of the sliding bar and all is well there, but in carbon 13, we wind up in a range, where there is bad contact. Changing the course adjustment (in our case from 77 to 78) on the C13 signal also helps to bring the fine adjustment at a spot where contacts are fine. 
In short, the sliding bar will have to be replaced.
Why was this not detected at Bruker. After talking with their personnel my understanding is that they have some virtual device for checking/adjusting tuning and matching, and this did not pick up the error. 

Anyway, I hope my entry was nevertheless of use, just in case anyone else runs into this problem in the future.

All the best,

Markus



Markus Hoffmann
Department of Chemistry
The College at Brockport 
State University of New York
Phone: (585) 395-5587
FAX: (585) 395-5805
mhoffman@brockport.edu


---- Original message ----
>Date: Mon, 4 Jan 2010 16:17:02 -0500 (EST)
>From: Bruker Users Mail <bruker-users-mail@chemistry.mcmaster.ca>  
>Subject: Odd behaviour with ATM equipped probe. (fwd)  
>To: undisclosed-recipients: ;
>
>Hello folks,
>
>Please find attached the description of an unusual problem with an ATM 
>equipped probe.
>
>__________________________________________________________________________
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>
>---------- Forwarded message ----------
>Date: Mon, 14 Dec 2009 15:32:48 -0500 (EST)
>From: Markus Hoffmann <mhoffman@brockport.edu>
>To: bruker-users-mail-request@chemistry.mcmaster.ca
>Subject: subscription request
>
>Dear Bob,
>
>I would like to be added to the bruker-users-mail-request.
>
>My name is Markus Hoffmann. I am an Associate Professor at The College at 
>Brockport, Department of Chemistry, a four-year liberal arts college, 
>where I keep our Avance 300 NMR instrument running. Our instrument was 
>installed in 2005 and runs under Topspin 1.3, patchlevel 8. As accessories 
>we have a 24 sample changer and variable temperature. The probe has 
>automatic tuning and matching capability and z-gradient coils.
>
><snip>
>  Under ATMM, to check tuning and matching for the X (13C) channel, the 
>signal disappears when I hit any of the "right arrow" keys for adjusting 
>matching and re-appears when I hit any of the corresponding "left arrow" 
>keys. We have a tuning rig here and I observe the same on the oscilloscope 
>of our tuning rig. Indeed, a 13C experiment would result in just noise 
>when we observe no signal under ATMM but in a normal spectrum when I leave 
>ATMM with a signal present. Fortunately, we also have a back-up dual probe 
>with which I replaced the ailing broadband probe. No problems here; we 
>could run in automation about 100 samples for our organic chemistry course 
>without any issues.
>
>All of these observations clearly suggest that there is something faulty 
>in the broadband probe. Yet, after having submitted for repair our probe, 
>the probe supposedly passed all tests, and a 13C spectrum print-out is 
>included in the case of the probe, which did arrive back today. However, 
>it behaves just the same as before we submitted it for repair. I observe 
>the exact same as described above.
>
>I am baffled. If it is not (really) the probe, and not any pre-amp etc. of 
>the console, what else is left to explain this? Did anyone else ever run 
>into anything like that?
>
>Thanks in advance for any pointers,
>
>Markus
>
>
>
>
>
>Markus Hoffmann
>Department of Chemistry
>The College at Brockport
>State University of New York
>Phone: (585) 395-5587
>FAX: (585) 395-5805
>mhoffman@brockport.edu

Received on Mon Jan 4 18:17:27 2010