This last time I disconnected both cables from the front AND the cable
going into the back of the preamp. No change.
Only when I set 2H lock to OFF in the acquisition parameters did the
oscillation disappear.
It is also present in the 15N wobb curve which is a separate channel on
this probe.
At this point I'm not sure how the lock signal is getting mixed up with the
other channels.
Ken Sharp-Knott
Manager of Analytical Services and the NMR Facility
Department of Chemistry
Virginia Tech
(540)267-6502 (Cell)
(540)231-0885 (Office)
________________________________
> From: main_at_ammrl.groups.io on behalf of Bob Berno via groups.io
> Sent: Thursday, May 30, 2024 3:02 PM
> To: main_at_ammrl.groups.io <main_at_ammrl.groups.io>
> Subject: Re: [AMMRL] Frequency ocillation in wobb curve on Prodigy TCI probe
Hello Ken,
I don't have a TCI Prodigy, but I suspect that you have a cold 2H preamp.
That means that you will have two cables for the 2H channel:
1.
A thick cable which probably has an N-type connection to screw to the probe.
This is carrying the "high power" RF from the lock amplifier.
2.
A thinner cable with BNC type connections which carry the signal from the cold
preamp back down to the 2H preamp slice beside your magnet.
When you say that you disconnected the lock cable, which one do you mean?
Or did you disconnect both? That could help explain where the oscillation
is coming form.
Bob.
Dr. Bob Berno
Manager: McMaster NMR Facility
Department of Chemistry & Chemical Biology
McMaster University, ABB-156
1280 Main Street West
Hamilton, ON L8S 4L9
(905) 525-9140 ext:24158
Fax: (905) 522-2509
http://macs.mcmaster.ca
> From: main_at_ammrl.groups.io on behalf of Kenneth Sharp-Knott via groups.io
> Sent: Thursday, May 30, 2024 2:05 PM
> To: main_at_ammrl.groups.io <main_at_ammrl.groups.io>
> Subject: Re: [AMMRL] Frequency ocillation in wobb curve on Prodigy TCI probe
Thank everyone for the tips!
Initially I tried the suggestion to disconnect the lock cable from the probe
and there was no change.
However, and strangely, if I turn the lock off - the frequency oscillation
goes away. So, it is lock related, but it's not coming down the lock cable
...
I feel this is a clue to the source of the problem... What's the source???!
Ken Sharp-Knott
Manager of Analytical Services and the NMR Facility
Department of Chemistry
Virginia Tech
(540)267-6502 (Cell)
(540)231-0885 (Office)
________________________________
> From: main_at_ammrl.groups.io on behalf of Akien, Geoffrey via groups.io
> Sent: Thursday, May 30, 2024 5:47 AM
> To: main_at_ammrl.groups.io <main_at_ammrl.groups.io>
> Subject: Re: [AMMRL] Frequency ocillation in wobb curve on Prodigy TCI probe
Hi Sameer,
We see this behaviour on the X channel on our filterless iProbe if you don’t
use the 2H stop-filter on the X channel (we specified this option at purchase
time so we could do 6Li experiments).
You can make it go away by using the RF filter, or by reducing the lock power
to lower than -15 dB or so. It doesn’t seem to matter too much what
frequency the X channel is tuned to.
If reducing the lock power isn’t enough to make it go away, then the
brute force option is turn the lock off and unplug the 2H channel e.g. on the
back of the preamp.
Thanks
Geoff
> From: main_at_ammrl.groups.io On Behalf Of Spin-Doc
> Sent: Thursday, May 30, 2024 8:03 AM
> To: main_at_ammrl.groups.io
> Subject: [External] Re: [AMMRL] Frequency ocillation in wobb curve on Prodigy TCI probe
Hi,
You could try to swap the SGUs to see whether that is the culprit.
Cheers
Bert
-> Sent via mobile <-
Spin-Doc
Magnetic resonance equipment, service, training & more
Dr. rer. nat. Bert Heise
Owner, applications scientist
Kiefernweg 13
58239 Schwerte
Germany
Web: http://www.spin-doc.net
Mail: bert.heise_at_spin-doc.net<mailto:bert.heise_at_spin-doc.net>
Phone: +49-171-5135315
Representing MestreLab, Stelar & Barthel HF
Am 30.05.2024 um 03:00 schrieb Bob Berno bberno_at_mcmaster.ca
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<mailto: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/
> From: main_at_ammrl.groups.io on behalf of Kenneth Sharp-Knott via groups.io
> Sent: Wednesday, May 29, 2024 3:19 PM
> To: ammrl_at_groups.io
> Subject: [AMMRL] Frequency ocillation in wobb curve on Prodigy TCI probe
I'm experiencing what looks like a frequency oscillation through the C13 wobb
dip. I don't see evidence of it in 1H or 2H wobb curves.
I was it was worse yesterday to the point that 13C sensitivity was significantly
reduced, which is what brought it to my attention. After a console reboot, computer
restart, cf, etc... Sensitivity seems to be about normal, but I'm still seeing this
oscillation.
Has anyone seen anything like this?
Ken Sharp-Knott
Manager of Analytical Services and the NMR Facility
Department of Chemistry
Virginia Tech
(540)267-6502 (Cell)
(540)231-0885 (Office)
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