Hey Spinlanders,
We’re chasing a difficult problem in our ARX 400. This machine is running XwinNMR 2.6 in Irix 6.5 on an SGI O2. When wobbing, setting the receiver gain, or acquiring data, the raw FID level is always a full 2000 scale units in the ACQU window. It flips from positive to negative in sync with the phase cycle, but the data is all at the same high level for both real and imaginary signals, and also for both high and low bands. The resulting average is always flat-lined at zero. If we run ZG and save the data, an octal dump (od) shows that there is only one line of zeroed data in the way-too-small fid file. Normal data files are much larger and have many, many lines of data. Data file is here:
arx400 16# od ./2/fid
0000000 000000 000000 000000 000000 000000 000000 000000 000000
*
0010000
We started by looking at the receiver signal – it is good, and there is an analog FID present at both inputs to the digitizer board. We have another ARX operating in another building, so we were able to swap some parts for troubleshooting. We tried changing the digitizer, and then ultimately the entire Aspect 3001 spectrometer card cage, entire digital card cage, receiver, router, host computer, hard drive and the data cable from Aspect3001 to AQI. Only the 2nd Ethernet card in the O2 has not been changed (need mac address for license). All of the PTS outputs are correct in amplitude and frequency, and the frequency switches correctly between Tx and Rx. All console power supplies are producing good voltages and no ripple. None of our changes have affected the symptoms, nor has testing uncovered anything abnormal except the final result!
We have not yet begun swapping internal console cables other than the AQI data cable, but other than that my shotgun is empty. Any other ideas what to try next, or what we have missed?
Thank you, -Hirsch
Jerry Hirschinger, NMR Instrumentation Specialist
Purdue Interdepartmental NMR Facility
560 Oval Dr. West Lafayette, IN 47907-2084
Office: Wetherill 365A
Phone / Fax: (765) 494-5288 / 494-0239
Cellular: (765) 427-3034
Received on Thu Oct 27 2016 - 05:45:48 MST