Hi Robert,
If the VXR has a gradient unit, one possibility for
that 60Hz noise could be from the gradient current.
Our previous DRX 600 had very similar 60 Hz noises,
later I figured out that Acrostar caused the problem.
After replacing the gradient unit, 60Hz noise was
gone. (If it is the case, you might do a quick check
by turning out the gradient, checking the
spectrum...).
Hoping this helps and happy holidays.
Bing Hu
--- Robert Harker <rharker_at_chem.ufl.edu> wrote:
> 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
> > begin:vcard
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> tel;fax:352-392-8758
> tel;work:352-392-4650
> x-mozilla-html:TRUE
> url:http://web.chem.ufl.edu/NMR/staff.htm
> org:University of Florida;Dept. Chemistry, NMR LABs
> version:2.1
> email;internet:rharker_at_chem.ufl.edu
> title:Engineer
> adr;quoted-printable:;;University of Florida Box
> 117200=0D=0ADept. Chemistry M/S
> 82;Gainesville;Florida;32611-7200;USA
> x-mozilla-cpt:;6736
> fn:Robert Harker ?2000 All Rights Reserved
> end:vcard
>
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Received on Wed Dec 27 2000 - 10:32:35 MST