1. Lock issueWrong phase vs Correct phase
    • For single deuterated solvent, it could be a lock phase issue if topspin complaint not able to lock. The red and green lock signals should reach the maximum first before going horizontal. If the signal reach the minimum first before going flat, the phase is 180 degree off. You may open BSMS window/lock page and then adjust the phase parameter.
    • For a mixture of two deuterated solvents, you will need to decide which solvent to be locked on, or create a new solvent in the solvent table. Locking on wrong solvent will result in wrong chemical shift measurements.

  2. Poor shimming result

    First of all, make sure you have a required volume of sample with sufficient amount of deuterated solvent. If not, it is very likely the shimming won't work well. The final B0 deviation should be below 1 Hz after shimming. If not, check whether the sample is inhomogeneous. Poor quality NMR tube, air bubbles, or insoluble substances can cause poor shimming. If the sample is fine, you may try to following options, then redo topshim.Fir

    • Use the Tune Before option "Z-X-Y-XZ-YZ-Z", even for a shigemi NMR tube
    • Start from a good shim file. Type "rsh" and choose the latest 3D shim file of the specific probe (File name: TS3D_XXXXXX), and then run topshim.
    • Manually optimize X, Y, XZ and YZ. After adjusting each dimension, optimize Z before moving to the next dimension.


  3. ADC overflow error
    Most likely the receiver gain/RG was set too high, causing poor quality spectra or no collected data. It may be necessary to type "ii restart" to reset the hardware after the error occurs.
    RG should be set to a low hundreds even if "rga" gave a much higher number. And always wait till the experiment finish the first scan before leaving the experiment running, just to make sure there won't be a "ADC overflow" issue.
  4. TopSpin won't start
    It is likely that the TopSpin is still open in somebody else's account. Rebooting the computer is the solution. To reboot the computer, please do it from the computer desktop/screen instead of pressing the power button on the computer case.
  5. CP800: Sample got stuck in the SampleMail system. Using TopSpin command "ej" or "ij" won't bring the sample down to the magnet or the sample injection compartment.
    The sample NMR tube is probably stuck on top of SampleMail vertical tube. You need to get on the platform, locate where the sample is. Note that the spinner can not be taken out from top of the delivery tube. You may carefully remove the sample NMR tube from the spinner, then unlock the mechanic switch (which holds the spinner) so the spinner can drop back to the injection compartment.
  6. CP600: Power outage ( during a thunder storm) caused Cryoprobe to warm up (emergency warmup mode); helium compressor stopped working.
    Once the system started to warm up, you may press cool-down button on one side of Cryp-Platform. If you does it quick enough, you may be able to force the system to cooldown instead of warmup, and the system will be ready for use in a few minutes. If it is too late and the system indicates that it needs to warm up first, then you will have to wait the system to warm up before you can cool it down. Overall it takes about  6 hours.
    In the emergency warmup mode, sample lift will also be activated, which can not be stopped until the system is completely warm or cold. Once the probe is warm or cold, you can uncheck the " Window locked" from the cryopanel windows, then close V13c (emergency lift).
    Emergency warmup mode may also switch off the heater unit. You should check/turn on the heater from Topspin temperature display window.
  7. A NMR tube appears too loose for the spinner, and/or good shimming is very difficult to achieve.
    It is possible that the NMR tube is not suitible for the 600 MHz or 800 MHz spectrometer. Please use high frequency (>=500MHz) NMR tubes. A temperary solution for a loose NMR tube is to put a thin strip of Scotch tape on the NMR tube where the spinner will hold the NMR tube, and careful push the NMR tube through the spinner.
  8. CP800: Poor resolution at high temperature
    One reason is that the sample may not have reached full equilibrium. Running a topshim before every long experiment is recommended. You may run a quick 1D experiment once in a while and compare with the previous ones. Another reason could be air flow flucturation. If you see unstable air flow, +/- 5 L/h to the setting air flow, please report to the facility manager.