Hi Ken,
I think Sameer may be on to something.
When I saw your WOBB curve, it reminded me of the WOBB I saw on a BBO probe
when we did not have the 2H-stop filter on the broadband preamp. So, in my
case I was seeing the lock signal making its way through to the broadband
preamp.
However, you have a TCI Prodigy cryoprobe. So you should have a dedicated
cold 13C preamp with a narrow bandpass filter. You should not be seeing any
2H signal on the 13C channel.
What happens if you turn the lock off? Using the “lock off”
command might not be enough, you may need to turn the lock power all the way
down too.
If the oscillation goes away, that you are getting interference from the
2H-channel.
Good luck,
Bob.
> From: main_at_ammrl.groups.io On Behalf Of Sameer Al-Abdul-Wahid via groups.io
> Sent: May 29, 2024 5:54 PM
> To: main_at_ammrl.groups.io
> Subject: Re: [AMMRL] Frequency ocillation in wobb curve on Prodigy TCI probe
Hi Ken and AMMRL,
We recently observed oscillations in the WOBB curve of all channels on a solids
AV II instrument, which we ultimately traced back to a failed LT1083CP
regulator on the 12V rail of the PSM3. The rail was outputting ~20V instead
of 12V. Frustratingly, the PSM3 LEDs were all lit even though the regulator
was faulty. Replacing the regulator fixed the problem.
However, since your issue is only on the 13C channel, I suspect our similar
symptoms have different causes. This may be a long shot, but if the calibrated
13C pulse width is longer, perhaps there’s an issue in the HPPR slice?
Best,
Sameer
--
Sameer Al-Abdul-Wahid, Ph.D. | Manager
Nuclear Magnetic Resonance Centre | University of Guelph
519-824-4120 Ext. 58914 | s.wahid_at_uoguelph.ca
http://nmr.uoguelph.ca/
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