Re: [AMMRL] CPI- cryoprobe had a fluctuating PreampHeat and Preamp Dev values

From: Michael Groves via groups.io <mgrovesnmr=yahoo.com_at_groups.io>
Date: Thu, 11 Dec 2025 23:05:56 +0000 (UTC)

 Hi Banghao,

-71 is pretty dang low.  I'm not sure if the diodes in the preamp will
even operate at that temperature...  I'm not sure if you've contacted
Bruker through the official channels but...  There is an adjustment for
this.  I don't think we normally recommend customers do this on their own. 
The best solution is likely going to be to call the service department and get
somebody back to take care of the issue that they caused.  If you haven't,
I would recommend you get in touch with rover_at_bruker.com or someone similar and
send in some logfiles so that they can have a look and make sure nothing is too
haywire before they recommend any adjustments.

Cheers,Mike
    On Thursday, December 11, 2025 at 10:35:24 AM EST, Banghao Chen via groups.io wrote:

  Dear all,

Our 700 MHz AVIII spectrometer with a CPI- cryoprobe recently had a fluctuating 
Preamp Heat and Preamp Dev values :After CP10-k replaced the coldhead, the preamp
temperature now reads ~71 K, which is much lower than the 77 K setpoint. 
Particularly, both Preamp Heat and Preamp Dev values are unstable and keep fluctuating.
We have tried many ways but could not resolve the issue.

Has anyone encountered a similar situation before? Your tips are appreciated. 

Best regards,BHC

******************************Banghao ChenNMR Facility Director
Distinguished University ScholarFlorida State UniversityDepartment of
Chemistry and Biochemistry102 Varsity Way, Tallahassee, FL 32306
chen_at_chem.fsu.eduo: (850) 644-3334



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Received on Thu Dec 11 2025 - 17:09:23 MST