Dear AMMRL members,
Our Varian 500MHz spectrometer has been showing a lock instability
problem for some time now and I haven't been able to find out what is
causing it. I though you may help me see "outside the box" on this
one. Here is what's going on,
The problem:
-After finding lock and making sure is not saturated, I click the
"lock on" button. The lock signal goes up and down and do not stay
still.
-The lineshape spectrum shows a couple of noise peaks (1.2-2 Hz) on
each side of the chloroform signal.
The troubleshooting:
a) Thinking that it may be a hardware problem, I have replaced the
following boards without success: Z0/Z1, lock xcvr, lock controller.
b) Thinking the it may be a vibration problem,
1) I have replaced the one-way helium valve from the magnet manifold.
2) I have added a manostat to better control the helium pressure.
3) The magnet got new TMC-legs (it had the rubber tires before) and
was moved to a new room.
c) Changing the lock response time (via software control) diminishes
the lock instability but it doesn't get rid of it.
Do you have any suggestions on where to look next?. It was suggested
to me before that the problem may be a vibration from the magnet
itself. What do you think about that?
Thanks in advance for all your help.
Carlos
______________________________________________________________________
Carlos A. Amezcua, Ph.D.
Biomolecular NMR
Manager
Tel: 214-645-2802
Biochemistry Department
Carlos.Amezcua_at_UTSouthwestern.edu
UT Southwestern Medical
Center http://
utswbionmr.swmed.edu
Received on Tue Oct 16 2007 - 19:41:51 MST