Re: [AMMRL] 4mm MAS3 Spinning Issues #Bruker #solids #Troubleshooting

Hi all,

We have a 400 MHz Avance III HD with a MAS3 unit and a K3166 solids probe (full name: MAS VTN400S1 BL4 N-P/H) that's been having some real problems while trying to spin.  A few months ago, when trying to spin, it would stop abruptly (or not even start spinning) and give the error: "A critical error occurred (Bearing Pressures).  Please get the logs and contact customer service".  (Also our MAS unit would sometimes be so bricked afterwards that I had to remove its battery for a few seconds to get it to start communicating again.)  I sent the probe into Bruker for repair.  They removed and cleaned the stator assembly, which was found to be dirty and tested the tune and spinning.  When I got the probe back, it worked flawlessly for one weekend of data collection, then started giving the Bearing Pressure error again.  Eventually, a Bruker service rep had me Tee the line from Bearing gas so that it fed back into the "Sense of Bearing" port on the MAS3... which seems to have fixed that error.  

But we are still having a problem with spin (or spin detection).  When I try spinning to 5000 Hz, it ramps up to about 1300 and then stops, eventually giving the error in the picture below:



I get this error even when I try spinning a newly-purchased, empty rotor with a laser score mark.   I've tried both without black Sharpie marker and with marker (opposite from the laser score mark) - neither works. 

It seems like maybe spin detection is not working.  Does anybody have any suggestions for how to "check the fiber optic at the probe" without ruining the alignment of the optic cables?  Or how to clean the fiber optic detection "window"?  Or anything else??? 

Thanks!

Wendy

Wendy Breyer, Ph.D.

Director of Instrumentation

Dept of Chemistry

Lehigh University