NT probe interface

Steve Philson (philson@nmr.chem.umn.edu)
Fri, 16 Dec 1994 17:37:56 -0600 (CST)

I would like to hear if anyone has suggestions about replacing the
probe interface boxes on our '81 vintage NT-300 spectrometer. We
still run it, mainly for pulsed field gradient diffusion measurements,
but occasionally for Si29 or Xe129. We replaced the console with a
Tecmag Libra system, and converted the magnet to a bottom-loading one,
with a couple of new probes. I would like to replace the ancient
probe interface boxes with something having better--not necessarily
state of the art--performance.

The NT probe interface is a pair of boxes, each with 4 plug-in modules
with various functions. It contains the observe and lock preamps, any
decoupler mixing (for homo-decoupling, not something we really need)
or filtering (for hetero), passive duplexing for the observe channel,
post-preamp attenuation, etc. I have replaced the lock preamp in one
of the boxes with a module from ARR, with some improvement in lock
S/N; I have also tried connecting external Doty or ARR preamps into
the observe channel, with some earlier success (lately I seem mostly
to blow things out). Since all the connectors to the probes are now
the wrong sort anyway, I would like to try to start from scratch, and
put together (or buy) a package to replace the whole thing. I do not
want to try to design anything, but since these are problems that have
been addressed by instrument builders for years, it should not really
be necessary. Maybe somebody out there has even done exactly this.

I can't justify my spending more than $2-3K on it, though the
principal user might be able to find some extra money for such an
upgrade.

Any thoughts?

-- 
Steve Philson		philson@nmr.chem.umn.edu
Director NMR Lab	612-626-0297
Chemistry Dept.		University of Minnesota