Antique electromagnet

Bill Gurley (bgurley@utk.edu)
Tue, 25 May 1999 13:13:30 +0000

One of my faculty members has a home-brew ICR instrument
that uses a very reliable Varian electromagnet from an old
HA-60 NMR. (I say it's reliable, because I have never had
to work on it in my 15 years here.) But now the field
controller is failing to control. When you turn on the
magnet, the field continues to rise past the set point until
finally the over-current switch kicks it off again. This is
one of the low-impedance magnets, using a "Field Dial"
controller that has a sensor on the pole face of the magnet
that we presume is a Hall probe.

Does anyone have any suggestions on how to test the Hall
probe, or other suggestions about the problem? In the
meantime, I am studying the manual and schematics.

Thanks,

-Bill-

Bill Gurley
Supervisor, Technical Services
Dept. of Chemistry, University of Tennessee, Knoxville