Shimming Techniques and Homogeneity Problems

Basic Shimming Techniques


Basic shimming techniques - starting from known shim values

When you are starting from a reasonable set of shim values the procedure for touching up the shims is straight forward. You should always verify how well your magnet is shimmed using the H1 Lineshape Sample (Chloroform in Acetone). This is the sample that is used when calibrating the instrument and verifying specs.

  1. Insert your sample and obtain lock, start the sample spinning. Make sure that your lock phase is optimized from the shim window. You can get the lock phase close using the lock window but you are pulsing the lock at a slower rate than when you are in the shim window.

     

  2. Optimize Z1. Increase or decrease Z1 to maximize your lock level.
    z1.gif

     

  3. To optimize Z2 you must either increase or decrease Z2 and then re-optomize Z1. Changing Z2 and looking for a maximum on the lock level will not properly set Z2. If you change Z2C 4-8 units and then optimize Z1 you should look for an increase from your starting lock level. If the lock level is higher, then continue to change Z2C in the same direction, optimizing Z1 after each change. If your lock level does not get back to the same level, try moving Z2C in the opposite direction and optimize Z1. You should do this until you can no longer increase your lock level.
    z2.gif

     

  4. The best way to adjust Z3 is to either increase or decrease Z3 and then repeat steps 2-3. The amount that you will need to change will depend on how wide the base of your lineshape peak is. If your peak is more than 30 hz at the .11% point you will need to make large changes in Z3 (about 64 units). If you are close to making spec then you will need to make small changes (2-4 units at a time) and repeat steps 2 and 3.
    z3.gif

     

  5. If your peak shows a hump (plateau) on either side you will need to adjust Z4. The size of the hump and the width of your base will determine how large of a change you will need to make. Change Z4 and then repeat steps 2-3. recheck your spectra, readjust Z4 as necessary and always repeat steps 2-3.
    z4.gif

     

  6. Normally you will not need to shim Z5. If your base is too wide and shimming Z1-Z4 does not help, then shimming Z5 may help narrow the base of your peak. After you make any changes to Z5 you must repeat steps 2-5. Z5 will induce a change in Z1-Z4 so they will need to be reshimmed after each change of Z5.
    z5.gif

     

  7. If your spinning sidebands are to high then you will need to adjust the non-spinning shims. Turn off your spinner, you may see a large drop in the shim level. The worse the shims, the larger the drop.You should optimize the non-spinning shims in the following order:
    X then Y (keep going back and forth until the lock level does not increase any more).
    X then Y then XZ then YZ (shim this in a loop. Continue until the lock is maximized.)
    X, Y, XZ, YZ, XY, X2-Y2, X3, Y3 (shim this as a loop)
    You can test your shimming by measuring non-spin lineshape or you can turn your spinner back on and recheck your spinning sidebands.

     

  8. Effects of Poor Shimming on Spectra
    badshims.gif

1001. How do I restart communication between the Sun host computer and the console?

The procedure varies by system:

For INOVA, MERCURY, GEMINI 2000, and UNITYplus systems:

  1. Open a shell tool window.

     

  2.  

     

  3. Press the reset switch or button on the console to reset the spectrometer.

     

  4.  

    If communications still has not restarted, do steps 5 through 10

     

  5.  

     

  6. Press the reset switch or button on the console to reset the spectrometer.

     

  7. Enter su to become superuser, enter the password, and then enter reboot .

     

  8. After the Sun finishes rebooting, log in as root and enter cd /vnmr/bin .

     

  9. Enter ./setacq and follow the directions on the screen.

     

  10. Log in as vnmr1 or another user. In the acquisition status window, the status should change from inactive to idle.

For UNITY and VXR systems:

  1. Open a shell tool window.

     

  2.  

     

  3. Press the reset switch or button on the console to reset the spectrometer.

     

  4.  

    If communications still have not restarted, do steps 5 through 13:

     

  5.  

     

  6. Enter su to become superuser and enter the password.

     

  7.  

     

  8. Power down the differential box and console.

     

  9. After two minutes, power up the console and power up the Sun computer.

     

  10. When the Sun memory test finishes, power up the differential box.

     

  11. After the Sun finishes rebooting, log in as root and change to the cd /vnmr/bin directory.

     

  12. Enter ./setacq and follow the directions on the screen.

     

  13. Log in as vnmr1 or another user. In the acquisition status window, the status should change from inactive to idle.

1002. How do I restart communication between the Sun host computer and the printer?

Start by cleaning the printer's spool file on the Sun:

  1. Open a shell tool window, enter cd /usr/ucb , and then enter ./lpc .

     

  2. When the lpc> prompt appears, enter clean all to clear all spool files.

If the Sun and printer are still not communicating, try deleting the existing printer files and then reinstalling the files. For instructions, refer to the manual VNMR and Solaris Software Installation. To find the information, look in the Table of Contents for the location of sections on printers and plotters.

1003. Why can't I get the configuration window to open?

This is probably a permission problem. To change permissions, do the following procedure:

  1. Exit VNMR and log in as vnmr1 .

     

  2. Open a shell tool window and enter cd /vnmr .

     

  3. Enter ls -l conpar . The following permission and ownership should appear:

    -rw-r--r-- 1 vnmr1 nmr

If the permission is different, enter chmod 644 conpar to correct it (only vnmr1 and root can change the permission of this file; only root can change the ownership). </>

1004. My VNMR window is broken, and the message "last menu not found" appears.

You probably need to become root and update user files. Do the following procedure:

  1. Exit VNMR, if it is running.

     

  2. Log in as root by opening a UNIX shell-tool and type su enter the root password. The prompt changes to #.

     

  3. Enter cd /vnmr/bin.

     

  4. Enter ./makeuser user , where user is a user name (e.g., ./makeuser vnmr1).

     

  5. Answer yes to questions on updating files.

     

  6. Log out from root and log in as the user (if not already). The VNMR window should be fixed.

1005. How do I change window size and background colors?

Use a text editor to change the default attributes of windows. To edit attributes, do the following procedure:

  1. Open a shell tool window and enter cd /vnmr/app-defaults.

     

  2. Open the file Vnmr with a text editor such as vi or textedit (e.g., textedit Vnmr).

     

  3. Edit the lines in the file to change the colors, fonts, etc. as you want.

Colors from other areas of VNMR can be changed here as well using the same procedure.

1006. What is the password for gradient shimming and other special features?

The password for gradient shimming was provided in a letter inserted with the manuals for the VNMR software (this password is no longer required on VNMR 6.1 or later). Passwords for other special features are included on a certificate that you receive when you purchase the software. Contact your sales representative for more information.

1007. How do I obtain patches for Solaris and VNMR? How do I load them?

Solaris patches:

If you are having problems with the Sun software and it appears that a patch might fix the problem, obtain the number of the patch (e.g., 103582-14, where the last two digits after the hyphen are the version number) and do the following steps:

  1. Open a shell tool window and enter showrev -p to display a list of Solaris patches already installed on your system. Note if the patch is already installed.

     

  2. If you still need to install the patch, check whether it is on the VNMR CD-ROM in the patch subdirectory. If so, enter pkgadd -d file to install it, where file is the full path to the patch file; for example, for the 103582-14 patch to Solaris 2.5.1 on the VNMR 5.3B CD-ROM, enter pkgadd -d /cdrom/vnmr_53b/patch/Solaris251/103582-14.

     

  3. If the patch is not on the VNMR CD-ROM, you can download it from Sun. Point your Web browser to ftp://sunsolve.sun.com/pub/patches and follow the directions on the screen.

    To download patches without a browser, enter ftp sunsolve.sun.com . At the Name: prompt, enter anonymous , At the Password: prompt, enter your email address. At the ftp> prompt, enter cd /pub/patches and then enter bin to use binary download instead of ASCII mode. To list files, use the ls command. To download files, use get with the name of the patch file. To leave FTP, enter the bye command.

    VNMR patches:

    To obtain patches to VNMR, point your Web browser to http://www.varianinc.com/nmr/products/software/vnmrpatches.html. To download patches, follow the directions on the screen.

1008. My floppy drive doesn't work?

Starting with Solaris 2.2, the usual method of accessing a floppy is to insert the floppy into the drive, enter volcheck in a shell tool window (or click Check For Floppy in the File menu of a File Manager window), and after a short time a File Manager window opens with the contents of the floppy. Click on Eject Disk in that window to eject the floppy.

If the usual procedure doesn't work, check that the line starting " Use floppy drive " is not commented out in the Volume Daemon Configuration File at /etc/vold.conf . Also check that the directory /floppy exists so that the floppy can mount on it.

1009. Why can't I print on a Lexmark printer?

For Solaris 2.x:

Lexmark can be set as one of the following: color plotter, no printer, or a B&W (no color) plotter and printer. Emulation is either HPGL or Postscript, but do not use automatic.

For SunOS 4.x:

Emulate the plotter as HP7550 and the printer as PS_X.

1010. How can I install a second hard disk?

The instructions are found in the manual VNMR and Solaris Software Installation . Look in the Table of Contents for the sections "Activating a Second Hard Disk After Solaris in Installed" and "External SCSI Devices."

1011. How can I get the correct partial integral display?

After the spectrum is transformed, do the following procedure

  1. Enter vp=20 to move up the vertical scale.

     

  2. Click on the Part Integral button.

     

  3. Click on the reset button to separate the partial integral from the full integral.

     

  4. Enter setint( int_number , value ) , where int_number is the number of the integral you want to select and value is the actual value of that integral (default is ins).

     

  5. Enter dpir to display the value of all integrals.

1012. Sample cannot eject, ejects too fast, or does not spin

  1. Check that incoming air line is about 25 to 45 psi, depending on the magnet.
  2. Insert a sample into the magnet.
  3. Enter e to eject the sample.
  4. Insert the sample and make sure it drops down softly with a cushion in the middle. The sample should have a double cluck sound when it settles at the bottom of the upper barrel.
  5. Turn on the spinning air with the computer command.

1013. No lock signal displayed on screen (INOVA and UNITY plus)

Perform the follow procedures on INOVA and UNITY plus systems if you open your ACQI window and the lock display is a flat line or just noise.

  1. Be sure that you have maximized lock power and lock gain, and that you have moved Z0 to the full range available.

     

  2. Check for a lock reading on the lock meter located on the remote status module.

     

  3. Eject the sample, and then reinsert the sample. Make sure the sample makes a double cluck sound as it settles at the bottom of the upper barrel.

     

  4. If you still do not have a lock, insert a sample with a strong lock signal (H1 lineshape or doped D2O) and high sensitivity, and run a single-transient proton experiment with the sw=100,000 and in='n' .

     

  5. Check that the magnet is still at field by moving a magnetic object slowly near the magnet, keeping a tight grip on the object. If you have lost the field, you will no longer feel a pull from the magnet


     

  6. Check that the power supply dc voltages are present and at the proper voltage.
     
  7. If still no lock, check the lock path. Divide the lock path in half by measuring the lock input to your probe. All signal levels are based on the lock power set to maximum. The Lock Preamp Probe Output (J5205) signal should have pulses of about 2 Vp-p (+10 dBm).

Testing the Transmit Portion of the Lock Path

Check the Lock Transceiver board as follows:

Testing the Receive Portion of the Lock Path

  1. Inject a signal at J5205 of the Lock Preamp. The signal must be at -75 dBm and at the system lock frequency. Use a signal generator to inject the signal.

    Alternately, if you have a dual-broadband system, you can use the output of Transmitter board #2 output for the signal as follows: Make the following changes to the experiment setup:

      dn='H2' dpwr=-16 dof=100 dm='yyy' dmm='c'

  2. Connect one end of a BNC cable to J298 of the N Channel Attenuator board. Connect the other end to a variable attenuator set to 6 dB of attenuation (or use a fixed 6-dB attenuator). Connect another BNC cable from the variable attenuator (or fixed) to J5205 of the Lock Preamp.

     

  3. Observe the lock screen in the ACQI window. You should observe a sine wave that changes as you change frequency. If you do not observe a signal on the Lock screen, then inject the signal directly into the Lock Transceiver board J229. This signal should be about -25 dBm, so you need to remove the variable attenuator and set dpwr=28 . Recheck to see if you have a signal on the lock screen.

1014. No lock signal displayed on screen

Perform the follow procedures on UNTY and VXR systems if you open your ACQI window and your lock display is a flat line or just noise.

  1. Be sure that you have maximized lock power and lock gain, and that you have moved Z0 the full range available.
  2. If you do not have the option lock meter, skip to the next step. Otherwise, check to see if you have a lock reading on the lock meter located on the remote status module.
  3. Eject the sample, and then reinsert the sample. Make sure the sample makes a double cluck sound as it settles at the bottom of the upper barrel.
  4. If you still do not have a lock, insert a sample with a strong lock signal (H1 lineshape or doped D2O) and high sensitivity, and run a single-transient proton experiment with the sw=100,000 and in='n'.
  5. Check that the magnet is still at field by moving a magnetic object slowly near the magnet, keeping a tight grip on the object. If you have lost the field, you will no longer feel at pull from the magnet
  6. Check that the power supply dc voltages are present and at the proper voltage.

Measurement Points and Signal Levels For Troubleshooting the Lock Path

If there is still no lock signal, you can divide the lock path in half by measuring the lock input to the probe. All signal levels are based on the lock power set to maximum. Check the Lock Preamp Probe Output J5205 signal for pulses at about 2 Vp-p (+10 dBm).

Testing the Transmit Portion of the Lock Path

Check the Lock Transmitter for the following values:

Testing the Receive Portion of the Lock Path

  1. Inject a signal at J5205 of the Lock Preamp. The signal must be at -75 dBm and at the system lock frequency. You can use a signal generator to inject the signal.

    Alternately, if you have a dual-broadband system, you can use the output of the Transmitter #2 board as follows: Make the following changes to the experiment setup:

      dn='H2' dpwr=1 dof=100 dm='yyy' dmm='c'

  2. Connect one end of a BNC cable to J3304 of the 2nd Broadband Transmitter board. Connect the other end to a variable attenuator set to 76 dB of attenuation. Connect another BNC cable from the variable attenuator to J5205 of the lock preamp.
  3. Observe the lock screen in the ACQI window. You should observe a sine wave that changes as you change frequency. If no lock signal, inject a signal of 6.251 MHz @ -30 dBm into J2404 of the Lock Receiver. Recheck to see if you have a signal on the Lock screen.
    • If you have a signal, you have a problem with the Lock Preamp.
    • If you do not, you have a problem with your Lock Transmitter or Input Board.

1015. No lock signal displayed on screen

Perform the follow procedures on MERCURY systems if you open your ACQI window and your lock display is a flat line or just noise.

  1. Check that you have maximized lock power and lock gain, and that you have moved Z0 the full range available.
  2. Eject the sample, and then reinsert the sample. Make sure the sample makes a double cluck sound as it settles at the bottom of the upper barrel.
  3. If you still do not have a lock, run an acquisition using a sample with a strong lock signal (H1 Lineshape or Doped D2O) and high sensitivity. After inserting the sample, run a single transient proton experiment with sw=100,000 and in='n'.
  4. Check that the magnet is still at field by moving a magnetic object slowly near the magnet, keeping a tight grip on the object. If you have lost the field, you will no longer feel at pull from the magnet
  5. Check that the power supply dc voltages are present and at the proper voltage.

Measurement Points and Signal Levels For Troubleshooting the Lock Path

If there is no lock signal, you can divide the lock path in half by measuring the lock input to the probe. All signal levels are based on the lock power set to maximum. Check the Lock Preamp Probe Output J5202 signal for pulses at about 250 mVp-p (+7 dBm).

Testing the Transmit Portion of the Lock Path

Check the Lock Transmitter board for the following values:

Testing the Receive Portion of the Lock Path

  1. Inject a signal at J5202 of the Lock Preamp. The signal must be at -75 dBm and at the system lock frequency.
  2. Observe the lock screen in the ACQI window. You should observe a sine wave that changes as you change frequency.
  3. If you still cannot observe a lock, inject a signal at -30 dBm into J85 of the Lock Receiver board with a blocking capacitor. Recheck to see if you have a signal on the Lock screen.

1016. No lock signal displayed on screen (GEMINI 2000)

Perform the follow procedures on GEMINI 2000 systems if you open your ACQI window and the lock display is a flat line or just noise.

  1. Check that you have maximized lock power and lock gain, and that you have moved Z0 the full range available.
  2. Eject the sample, and then reinsert the sample. Make sure the sample makes a double cluck sound as it settles at the bottom of the upper barrel.
  3. If you still do not have a lock, run an acquisition using a sample with a strong lock signal (H1 Lineshape or Doped D2O) and high sensitivity. After inserting the sample, run a single transient proton experiment with sw=100,000 and in='n' .
  4. Check that the magnet is still at field by moving a magnetic object slowly near the magnet, keeping a tight grip on the object. If you have lost the field, you will no longer feel at pull from the magnet
  5. Check that the power supply dc voltages are present and at the proper voltage.

Measurement Points and Signal Levels For Troubleshooting the Lock Path

If there is still no lock signal, you can divide the lock path in half by measuring the lock input to the probe. All signal levels are based on the lock power set to maximum. Check the Lock Preamp Probe Output J5202 signal for pulses at about 250 mVp-p (+7 dBm).

Testing the Transmit Portion of the Lock Path

Check the Lock Transmitter for the following values:

Testing the Receive Portion of the Lock Path

  1. Inject a signal at J5202 of the Lock Preamp. The signal must be at -75 dBm and at the system lock frequency.
  2. Observe the lock screen in the ACQI window. You should observe a sine wave that changes as you change frequency.
  3. If you still cannot observe a lock, inject a signal at -30 dBm into J2853 of the Lock Receiver board with a blocking capacitor. Recheck to see if you have a signal on the Lock screen.

1017. No NMR spectrum or noise only on the screen

  1. If you have a lock signal, change the value of parameter tn to another band.

    For example, if you took a proton acquisition and your spectrum showed noise only, change the setting tn='C13' or set up your standard C13 parameters and take an acquisition using a sample that you know will have C13 peaks (use the C13 sensitivity sample).

  2. Measure the transmitter pulses at the probe input. The point to measure depends on the frequency of the system. General test points are used in this explanation. Assuming that you have no spectra for either band, set up to pulse the probe and measure at the proton input to the probe. Set up your parameters as follows:

    at=.1 pw=10 sw=5e4 bs='n' dm='n' nt=1e6 tn='H1' tpwr=63

    Connect a cable through a 30-dB attenuator from your oscilloscope to the probe output of the preamp. Start the acquisition by entering go on the VNMR command line.

  3. Set the scope time base so that you can view a 10-microsecond pulse. The amplitude of these pulses should be about 2.5 to 5 Vp-p.
  4. Check the power supply dc voltages. It is possible that one of the voltages is low or missing.

Depending on your instrument, different procedures are required to trouble shoot further.

The following procedure is for UNITY INOVA or UNITYplus only

Measurement Points and Signal Levels for Troubleshooting the Transmitter Path

If there is no transmitter signal at the probe, start by following the signal back or bracket the path to divide the transmit path even further. All signal levels are based on the transmitter power set to maximum ( tpwr=63).

Transmitter Path Measurement Points ( UNITY INOVA or UNITYplus )

Transmitter #1 (these signals are measured straight into the scope)
P2X4 Synth Input: 2 Vp-p (+10 dBm)
J2X5 LO Output: 2 Vp-p (+10 dBm)
J2X3 Xmtr Output: 2 Vp-p (+10 dBm)
N Channel Attenuator
J297 Channel A Output: approx. 1 Vp-p (+4 dBm)
J298 Channel B Output: approx. 1 Vp-p (+4 dBm)
AMT #1
J4073 Channel A Output: +12 - +17 dBm (measured through a 30-dB attenuator)
J4072 Channel B Output: +24 - + 26 dBm (measured through a 30-dB attenuator)

You should see about 60-dB gain across the AMT amplifier. To verify this gain, you must measure both the input and output at the AMT amplifier.

Testing the Receive Path ( UNITY INOVA or UNITYplus )

  1. Inject a signal at probe input of the preamp. The signal must be at -75 dBm and at the transmitter frequency. Use a signal generator to inject the signal.

    Alternately, if you have a dual-broadband system, you can use output from the Transmitter #2 board as follows:

    • Make the follow changes to the experiment setup

      dn='H1' dpwr=-16 dof=100 dm='yyy' dmm='c'

    • Connect one end of a BNC cable to J297 of the N Channel Attenuator board. Connect the other end to a variable attenuator set to 6 dB of attenuation (or use a fixed 6-dB attenuator). Connect another BNC cable from the variable attenuator (or fixed) to the probe port of the preamp.
  2. Once you have injected the signal, take an acquisition. You should observe a peak in your spectra. If you do not observe a signal on the spectra, inject the signal directly into the mixer (J5105). If you still do not observe a signal on the spectra, inject a 10.502 MHz (-30 dBm) signal directly into the Observe receiver J249.

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The following procedure is for UNITY or VXR only

Measurement Points and Signal Levels for Troubleshooting the Transmitter Path

If there is no transmitter signal at the probe, start by following the signal back or bracket the path to divide the transmit path even further. All signal levels are based on the transmitter power set to maximum ( tpwr=63).

Transmitter Path Measurement Points (UNITY or VXR)

Transmitter #1 (these signals are measured straight into the scope)
P3206 Synth Input: 2 Vp-p (+10 dBm)
J3202 LO Output: 2 Vp-p (+10 dBm)
J3204 Xmtr Output: 4 Vp-p (+16 dBm)
AM/PM Xmtr Output: 2 Vp-p(+10 dBm)]
AMT #1

 
Channel A Input: approx. 0.6 Vp-p (+0 dBm)

 
Channel B Input: approx. 0.6 Vp-p (+0 dBm)
J4073 Ch A Output: +12 - +17 dBm (measured through a 30-dB attenuator)
J4072 Ch B Output: +24 - + 26 dBm (measured through a 30-dB attenuator)

You should see about 60-dB gain across the AMT amplifier. To verify the gain, measure both the input and output at the AMT amplifier.

Testing the Receive Path (UNITY or VXR)

  1. Inject a signal at probe input of the preamp. The signal must be at -75 dBm and at the transmitter frequency. Use a signal generator to inject the signal.

    Alternately, if you have a dual-broadband system,you can use the output of the Transmitter #2 board as follows:

    • Make the following changes in the experiment setup

      dn='H1' dpwr=0 dof=100 dm='yyy' dmm='c'

    • Connect one end of a BNC cable to J3304 of the Broadband Decoupling board. Connect the other end to a variable attenuator set to 6 dB of attenuation (or use a fixed 6-dB attenuator). Connect another BNC cable from the variable attenuator (or fixed) to the probe port of the preamp.
  2. Once you have injected the signal, take an acquisition. You should observe a peak in the spectra. If you do not observe a signal on the spectra, inject a 10.502 MHz (-30 dBm) signal directly into the Observe Receiver J2602.

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The following procedure is for MERCURY only

Measurement Points and Signal Levels for Troubleshooting the Transmitter Path

If there is no transmitter signal at the probe, starty by following the signal back or bracket the path to divide the transmit path even further. All signal levels are based on the transmitter power set to maximum ( tpwr=63).

Transmitter Path Measurement Points (MERCURY)

HI BAND Transmitter Board (these signals measured straight into the scope and P66 REF IN 0.9 Vp-p (+3 dBm) SMB to BNC connector)
J62 LO Output: 0.6 Vp-p (+0 dBm)
J63 Xmtr Output: 0.7 Vp-p (+1 dBm)
LOW BAND Transmitter Board
P44 REF IN: 0.9 Vp-p (+3 dBm)
J42 LO Output: 0.6 Vp-p (+0 dBm)
J43 Xmtr Output: 0.7 Vp-p (+1 dBm)
AMT Amplifier
J207 Ch. A Output: +12 - +17 dBm (measured through a 30-dB attenuator)
J211 Ch. B Output: +24 - + 26 dBm (measured through a 30-dB attenuator)

Testing the Receive Path (MERCURY)

  1. Inject a signal at probe input of the preamp. The signal must be at -75 dBm and at the transmitter frequency. Use a signal generator to inject the signal.
  2. Once you have injected the signal, take an acquisition. You should observe a peak in your spectra. If you do not observe a signal on the spectra, inject a -30 dBm signal through a blocking capacitor directly into the observe receiver, J54 for High Band or J55 for Low Band.

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The following procedure is for Gemini only

Measurement Points and Signal Levels for Troubleshooting the Transmitter Path

If there is no transmitter signal at the probe, start by following the signal back or bracket the path to divide the transmit path even further. All signal levels are based on the transmitter power set to maximum ( tpwr=63).

Transmitter Path Measurement Points (Gemini)

1H Transmitter board (these signals are measured straight into the scope)
J2602 LO Output: 2 Vp-p (+10 dBm)
J2603 Xmtr Output: 20 Vp-p (+30 dBm) [400 MHz @ 2 Vp-p (+10 dBm)]
13C Transmitter board
J2702 LO Output: 2 Vp-p (+10 dBm)
J2703 Xmtr Output: 20 Vp-p (+30 dBm)
Broadband Transmitter board
J2702 LO Output: 2 Vp-p (+10 dBm)
J2703 Xmtr Output: 2 Vp-p (+10 dBm)
1H/13C Pulse Amplifier board
J2904 1H Output: +10 dBm @ 200 MHz, +14 dBm @ 300 MHz (through a 30-dB attenuator)
J2902 13C Output: +10 dBm (measured through a 30 dB attenuator)
Kalmus Amplifier
J2904 1H Output: +20 dBm (measured through a 30-dB attenuator)
J2902 13C Output: +22 dBm (measured through a 30 dB attenuator)

Testing the Receive Path (Gemini)

  1. Inject a signal at probe input of the preamp. The injected signal must be -75 dBm at the transmitter frequency. Use a signal generator to inject the signal.
  2. Once you have injected the signal, take an acquisition. You should observe a peak in your spectra. If you do not observe a signal on the spectra, inject a -30 dBm signal through a blocking capacitor directly into the observe receiver, J54 for High Band or J55 for Low Band.

1018. Magnet is iced up or forming ice from the neck tube

  1. Check if the whole magnet is very cold. A very cold magnet means that the magnet has lost its vacuum. Obtain help from a Varian service engineer.
  2. If the magnet temperature is normal and only the neck tube is iced up, the cause is ice blocked by the pressure relief valve or inside the neck tube.

1019. Flow meter gauge reading is very high

  1. This may be an indication of low on cryogens. Check and measure the actual level of the LN2 and LHe. Fill up cryogens if necessary.

     

  2. Check the flow meter gauge on HE. If it reads high or is erratic, this may indicate the LN2 is dry. Fill up the LN2.

     

  3. Check the flow meter gauge on N2. If it reads high or is erratic, this may indicate the magnet losing vacuum. Get Service Engineer help.

1020. Reading diagnostic messages from console

You can use a dumb terminal or a personal computer as a terminal:.