Dear Randy,
This has been observed by us as well. We found that we were using very
high decoupler power. Reduce dpwr to arround 40 to 43 and rerun the
experiment. This would solve the problem.
Best Luck !
L.S.Mombasawala.
NMR Lab, RSIC,
Indian Institute of Technology,
Powai, Mumbai 400 076
___________________________________________________________
On Tue, 20 Apr 2004, Randy Winchester wrote:
> AMMRL Group:
>
> I have a question about a Varian Innova 400 that was recently installed
> (It is about 1 year old and we had it moved here this winter). One week
> ago the installation was just about complete and we had z1 and z2
> cryoshims quench. Of interest is that the instrument had passed all
> specs including bb decoupled 13C at this point.
>
> Well, this week the engineer returned and reset the cryoshims and
> touched up the shim files and was getting ready to go and now we have a
> problem that we cannot solve. When acquiring a decoupled carbon the
> lock level drops from 90 down to 10 and eventually is unregulated.
> Stopping the acquisition leads to the lock signal returning. Running a
> coupled spectrum or proton is fine, eg no loss of lock. APT leads to a
> loss of lock.
>
> Questions:
>
> Does this sound like we are missing a filter?
> Could someone that has observed this behaviour before give me a few
> ideas of where to start looking?
>
> Thanks!
>
>
>
>
> Randy Winchester
> Department of Chemistry
> Grand Valley State University
> Allendale, MI 49401
>
> 616-331-2387
> 616-331-3230 (fax)
>
> winchesr_at_gvsu.edu
>
>
Received on Thu Apr 22 2004 - 13:46:01 MST