Hi Scott,
are both 400MRs using a synthesizer board (to the right of the leftmost RefGen
board) or are they using a 19" VFS synthesizer module?
The synthesizer boards are known to be a source of problems. May be worthwhile
testing the other channel by swapping the RJ45 as well as BNC plugs between Ch1/2.
Did you check all voltages on the Molex plugs in the bottom right side of the
console? Any browning on any of the power supply pins?
Best regards
Bert
> Am 27.03.2024 um 18:40 schrieb Smith, Scott K <scott.smith_at_austin.utexas.edu>:
>
> 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
>
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Received on Wed Mar 27 2024 - 16:27:27 MST