AMMRL;
We have been trying to track down a stubborn 60 Hz noise problem in our
VXRs300. The noise presents itself as side bands to the main signals in
the spectra 60 hz on each side. They are randomly out of phase with the
main signal and the 2 side bands are 180 degrees out of phase with each
other. Since they are randomly phased in relation to the main signal,
ncreasing the NT eventually cancels most of it out. This doesn't help
when we are attempting an auto shim routine which uses only one
transient. The side bands are sometimes more than 5% of the main signal
so this introduces error to our shim routines.
I've checked out the power supply, PTS 160 and many of the cards in both
the RF and digital card cages. The problem remains regardless of probe
or nucleus observed.
Varian support hasn't been much help ... I thought since the discussion
in AMMRL has been related to noise lately that maybe my query will
solicit an "AHA! I remember when our VXR did that and it was the ____"
Thoughts and suggestions please.
Thanks in advance,
Robert Harker
Received on Thu Dec 21 2000 - 13:29:19 MST