Dear All,
Our Avance I 500MHz spectrometer has experienced two problems within a short
period that may or may not be related. Auto-lock began to fail occasionally
earlier this year, and often a second attempt would succeed at locking and
auto-gain. Sometimes resetting the BSMS, running cf, etc. would seem to help.
About 6 weeks ago, the lock failed altogether. Numerous attempts at resetting
the console, re-starting topspin 2.1, etc. were not effective at restoring
function. A couple of weeks ago, I was able to find a signal using the BSMS
control window, by adjusting the sweep amplitude, field and lock phase, so
I could clearly see a noisy lock signal scaled, and phased properly. I was
able to ‘lock’ manually, but the signal was very weak and noisy, and
topshim repeatedly failed, with an error indicating signal too weak. The
next day, I could not repeat the manual lock, and the lock signal was a
flat line at baseline. Of course, I checked to see if there was a magnetic
field, which there is.
Throughout this time, tuning was fully functional, until about two weeks ago,
when the wobble became very weak for 1H, and failed altogether on the BB,
and other channels. Proton had the only ‘observable’ dip, but manually
adjusting the tuning knob on our QNP probe did not change the frequency,
and match did have limited function, but the signal is again extremely weak.
The other channels give only noise.
We have now checked the lock transmission path from the spectrometer to the
HPPR/2 preamp, using an oscilloscope, and found that there is a clear and
steady pulse train signal from the lock transmitter to the lock-in connector
on the HPPR/2 (~350-400mv). However, there is no lock tx signal observed
passing through to the probe side of the HPPR/2 (by oscilloscope), and no
signal detected on the lock out side of HPPR/2 with all normal connections
re-established to the probe. (Note: this test was done with the QNP probe
installed).
We also checked to see if low power signals produced with wobb were observable
for 13C through the cable to the 13C module of HPPR/2. There were clearly
observable signals at the HPPR/2 end of the transmission cable by oscilloscope,
but again, no 13C tuning signal observed by the spectrometer with all cabling
connected. Only noise was detected by wobb 13C, with or without cables connected
to HPPR/2.
I tried changing probes as part of the troubleshooting process. ATMA fails
consistently, and atmm shows no signal on our newer generation TXI probe,
which has autotuning capability. The locking and shimming failures are
identical for both probes. Another note is that the QNP probe was recently
repaired to restore a failed carbon channel and a short, and has otherwise
been working great ever since.
Can anyone suggest a next course of action to further isolate the source of
the lock and tuning failures? Our sense is that the HPPR/2 stack is the
culprit, and possibly the cover module in particular?
Thanks and best wishes,
Bill
William Hiscox, Ph.D.
Assistant Professor
Department of Translational Medicine & Physiology<
https://medicine.wsu.edu/dcp/translational-med/>
Elson S. Floyd College of Medicine
Washington State University, Spokane
medicine.wsu.edu
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Received on Thu Jul 31 2025 - 10:25:19 MST