Broken Tube in the Magnet:

Console is unresponsive to Commands:

1. With the right mouse button, click once on the Solaris desktop background to reveal a menu.  Click on Programs or Tools, then over to select Terminal… A Terminal window will pop-up.

2.  In the Terminal window, type ‘su acqproc’ and hit Return.  You will get a message indicating that acqproc is being ‘killed’.  Also, in the ACQUISITION STATUS window in VNMR, STATUS should now read “inactive”.

3. Proceed to the NMR console, which is the big grayish box.  See below for location of reset button for various instruments.

4. Push the reset button.

LOCATION OF RESET BUTTON FOR EACH INSTRUMENT
Instrument	Reset Button Location
I400: Inova-400	Open the left door of the consolle. Look for the switch with the written word,'reset'.
Mercury 400

5. Wait for at least 40 seconds.

6. In the terminal window type su acqproc and hit Return.  This will take a few moments.   Look at the ACQUISITION STATUS window in VNMR.  Wait for STATUS to read “idle”.

7. In the VNMR command line (i.e. where you usually type e), type su and hit Return.  The NMR should now be ready for use. 

 

Can't Lock on Sample: (PDF version)

This can be caused by several problems. Common reasons and their solutions are listed below:

Common Reasons for Inability to Lock
Cause	Result	Solution
No deuterated solvent	No deuterium signal to lock on.	Use a deuterated solvent like CDCl3.
Shimming is very poor	The signal is so broad that it is not well observed.	Type fixshims to get a good start.
Suspended particles	This causes line broadening, which makes the signal intensity weaker.	Filter your sample.
Too concentrated	There is little deuterated solvent to get a lock. Especially problematic when using CDCl3.	Dilute your sample or use a solvent with more deuteriums (e.g. C6D6).
Improperly gauged	When injected, the sample is not in the coil.	Eject sample and ensure that the sample resides between the white lines on the gauge.
Lockpower is too low	The sample is not receiving enough rf signal to flip the deuterium spins.	Increase lockpower to 80% of max before trying to lock.
Lockpower is too high (for multi-resonance samples)	With solvents having more than one deuterium resonance (e.g. CD3OD, THF-d8), high lock power will cause all resonances to be excited. This makes locking on a single resonance difficult.	Reduce the lockpower by 20 and find the lock signal. If you see the signal with 'bumps', reduce lockpower further.
Lockgain is too low	The signal from your sample is not amplified enough for you to see the signal.	Increase Lockgain to maximum.

• If the above table does not resolve your problem, try locking on a pure sample of C6D6.
  • Once you are able to lock on the benzene-d6, shim as well as you can.
  • Replace the benzene-d6 sample with your sample and attempt to lock.
  • Still can't get a lock? Contact the staff.

I Can't Access a Workspace (e.g. exp1, exp2):

• The usual message you will get is,'foreground processing is active.'
• A locked experiment is a result of improper logging-off by a user. Remember to always exit VNMR prior to exiting the User session!
• To unlock and gain access to an experiment:
  • Type unlock(#,'force'), where # is the number of the locked experiment. For example, I try to access exp1 by typing jexp1 and I get the 'foreground processing is active' message. I would then type unlock(1,'force'). Exp1 is now available.

I Can't Eject my Sample:

• This is usually a result of a failure in the acquisition computer. You need to see if the acquisition computer is active.
• Look at the ACQUISITION STATUS window and see if the Status is Idle, Acquiring, or Inactive.
  • If it is Acquiring, type aa. If you get the message similar to,'no experiment is active', you will need to reboot the acquisition computer. Use the procedure for a unresponsive console. Click here to view reboot procedure.
  • If it is Inactive, you will need to reboot the acquisition computer. Use the procedure for a unresponsive console. Click here to view reboot procedure.
  • If it is Idle, try typing exit. Wait about 1 minute. If you are not exited from the VNMR program, you will need to reboot the acquisition computer. Use the procedure for a unresponsive console. Click here to view reboot procedure. If you are exited, click on the VNMR icon and type su, then try ejecting again. Still can't eject? Try to reboot the acquisition computer. Use the procedure for a unresponsive console. Click here to view reboot procedure.
• If rebooting does not work, contact the NMR staff!

Poor Shimming: (Click HERE to get a more detailed procedure for shimming. PDF format)

• Poor shimming or more properly, poor lineshape, can be a result of many factors. Below is a list of common causes and their remedies:

• If shimming problems are not resolved, contact the NMR staff.

Poor Signal/Noise:

• Signal/Noise (S/N) improves as the square root of nt. Increasing the number of scans will improve S/N up to a point. Maximum improvement in S/N occurs early in the experiment. Diminishing returns are acheived with larger number of scans.
• Increasing concentration is an obvious fix if you have enough sample. But be careful not to get too concentrated because linebroadening will occur at higher concentration.
• Many of the same problems with poor shimming result in poor signal/noise. If you don't get better S/N after trying the shimming procedures, contact the NMR staff.

The Computer Screen is Blank:

• Try moving the mouse to see if the screen saver is activated.
• Make sure the monitor is turned on.
• If this does not fix the problem, contact the NMR staff.

The Temperature is too High/Low:

• Type temp=26.2 su (Mercury) or temp=24.6 su (Inova). This will reset the temperature controller to 25 degrees Celsius.
• If this does not work, type temp, click RESET, wait until VT controller has reset, and set the temperature in the pop-up window by dragging the slider.
• If this does not work, type temp='n' su. This should turn off temperature control.
• If the temperature is still incorrect, contact the NMR staff.

My Sample is not Spinning:

• Check to make sure that spin is turned on by clicking Acqi=>LOCK. Check the spin setting at the bottom of the window. Adjust the spin rate to 20. To the right of Spin:, click off, then click on. If it still is not spinning, then...
  • The most common cause of this problem is a dirty spinner or a improperly gauged sample.
  • Eject the sample and clean the spinner with a Kim wipe and isopropanol. Make sure you clean the narrow portion of the spinner.
  • Regauge the sample. IMPORTANT: Always hold the spinner and sample at the fat part of the spinner. Holding the sample and not the spinner may cause the spinner to slip, which will make shimming difficult.
  • Insert the sample. If it still does not spin, contact the NMR staff. Please fill out a NMR Incident Report.

My baseline rolls or is not flat (for 2D Spectra, see the Processing, phasing, and plotting 2D phase sensitive data Handout):

• There are several possible causes of this problem:
  • Too high receiver gain can cause severe distortions to the baseline that cannot be corrected. If this is the problem, you should of seen the error message 'Reciever Overflow' or 'ADC Overflow' during the experiment. The easiest fix is to enable autogain (default setting) by typing gain='n' and rerunning the experiment. Arrayed experments like pulse width determination or kinetics do not allow autogain so you must set it manually. Type gain=gain-6 and rerun the experiment (one scan will be sufficient to check for errors). If errors still occur, reduce gain and repeat experiment. Continue with command until no error is shown. If you've reduced the gain to the minimum and still get an error, reduce the pulse width (e.g. type pw=pw/2).
  • If your spectral window is too narrow, peaks outside that window will be 'folded' or aliased because they were not properly sampled (they need to be sampled at twice their frequency, see Nyquist theorem). These peaks will typically appear as out-of-phase peaks folded into the opposite side of the spectrum. For example, my spectral window is set for 10 ppm to 0 ppm and I have a carboxylic acid with a peak at 13 ppm. Since the 13 ppm peak is outside my window it will appear as a distorted peak at 3 ppm (0 ppm +(13 - 10 ppm). To correct this, increase the spectral window by typing setsw(upper desired ppm #,lower desired ppm #) [e.g. type setsw(15,0)].
  • A rolling baseline can be a result of improper phasing due to a failure of autophasing (usually because the S/N is too low for the automation to work properly). You should reset the phasing parameters and start over. Type lp=0 rp=0 to return zero- and first-order phasing to their initial positions. Follow the manual phasing procedure detailed here.
  • A crooked but flat baseline is due to a slight offset in the quadrature detectors. To correct, type f full cdc dc. This will make the edges of the spectrum horizontal. Do not use if you have a peak at the edge of the spectrum. You'll need to increase the spectral width and repeat the experiment.