Dear Rob
how far out did you increase the pulse. It could be either the amplifier not
putting out the right level or it could be the probe not taking it. If the
probe does not take the power it is usually not stead but rather erratic.
If you are able to calibrate a, albeit longer, pulse at lower power setting
it points toward the probe.
You should probably test much longer pulses to see if there is just low
amplifier output. Instead of linearly increasing the duration just double
it until you are beyond the 180.
Is the probe tuned?
Best regards
Clemens
On 10/5/2026 11:38 AM, Robert Lewis via groups.io wrote:
We recently resurrected our Oxford Pulsar 60 MHz benchtop. Oxford Instruments
installed a new power supply which breathed life into it. The set up procedure
tuned and matched OK but the 90 degree pulse calibration gave a steadily
increasing signal, not the usual sinusoidal output. I would like to be more
certain of the fault diagnosis before asking Hull University to cover the
cost of another engineer's visit. The Pulsar has reached the, no parts
guaranteed stage. Chemistry at Hull was closed a couple of years ago, with
the loss of all academic staff. There has just been another voluntary exit
scheme so I am trying to keep a low profile and fix things on the cheap.
Does this fault sound like an Rf power issue or a pulse length issue. Are
there any experiments that might provide a clue? Any suggestions, gratefully
received. Are there any Pulsar circuit boards out there looking for a home?
Rob Lewis
NMR guy at Hull University
Glory days, home of the first stable liquid crystals
--
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Clemens Anklin Ph.D. Vice President
Bruker BioSpin NMR Applications & Training
15 Fortune Drive NEW Phone: 978-313-5NMR(5667)
Billerica MA 01821 bluesky: _at_canklin.bsky.social
web: http://www.bruker.com
e-mail: clemens.anklin_at_bruker.com
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Received on Mon Oct 05 2026 - 09:25:43 MST