I am sure nearly everyone has had to track down a missing signal.
In this case the root cause in somewhere in the MR400's LO switching device.
The MR has a single receiver box for both channels. The LO used in detection
is pre-selected by an external module (Mini Circuits RF switch ZASWA-2-50DRA+).
In short, this switch is no longer passing through high band LO to the receiver
making it appear that there is no signal. It looks like the LO for low band
channel is passively allowed through, so one gets the curious result that a carbon
spectrum with full proton decoupling can be acquired while nothing not even tuning
works on the high band channel. All the transmitter pathways checkout as do the
LO's themselves. Proton work if I manually swap the LO input cable directly to
the receiver.
Are these mini circuit devices known to just quit working? Or might there
be a problem with the power-supply and TTL control lines feeding the switch?
I now have two MR's with this error.
I would appreciate any suggestions or help I can get at this point.
Cheers,
Scott
Scott K. Smith, Director of NMR Spectroscopy
The University of Texas at Austin | Chemistry | 832-294-1928 | utexas.edu
https://www.utexas.edu/
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Received on Wed Mar 27 2024 - 10:55:23 MST