(These instructions assume you are familiar with basic Macintosh procedures, if you are not, see a Macintosh manual or the tutorial which is on most Macintosh computers. Throughout the following, MB means mouse button.)
Get assistance the first time that you do this.
If you wish to adjust the sample temperature below room temperature, the probe gas must be changed from air to nitrogen. If you wish to adjust the sample temperature above room temperature, go to the next paragraph. Obtain a nitrogen gas source and attach it to the regulator located near the left rear portion of the left spectrometer cabinet. Turn on the N2 flow and adjust the regulator to 40 psi. Open the Console window and then, if necessary, the AIR window. Move to the circle to the left of N2 and click the MB to switch the probe gas from air to N2, also make sure VT air and Body air are active. After N2 has flowed through the probe for a few minutes, put the VT gas coil (located on the floor next to the magnet) into a cold bath (dry ice in isopropanol or liquid N2).
Open the left door of the right spectrometer cabinet and look at the VT Air valve (second from left) at the bottom of the cabinet. The top of the ball should be at 30 on the gauge, if it is not adjust the valve with the black knob. Move the cursor to the VTGN icon located on the right side of the desktop and double click the MB to start the VT routine. If you will be working above room temperature set the Upper Limit 10 degrees above the desired working temperature. If the desired temperature is below room temperature, set the Upper Limit to 35 degrees. Make sure the Lower Limit is set to the lower of the following two values: 0 or at least 10 degrees below the desired working temperature for all cases. Change the Set Temperature to the desired working temperature. Move the cursor to the toggle switch and click the MB until the toggle points toward VT Operate. If there is no response from the VT unit, toggle back to VT Standby and then back to VT Operate again. Note that the Actual Probe Air Temperature on the screen should be divided by 10 to get the true temperature. Another temperature display is located inside the left door of the right console. Do not exit the VT window during VT operation. When you are ready to acquire data, bring the main MacNMR window to the top of the desktop.
When you have completed low temperature work, set the temperature to 20 degrees, thaw the tube from the cooling coil to the probe if necessary with the heat gun. Be careful, movement of the frozen tube may cause the probe VT dewar to break; also be careful with the heat gun, it will be attracted to the magnet. Remove the coil from the cold bath and warm it with the heat gun. Allow N2 to flow through the probe for another 15 minutes. Go to the VT window and toggle to VT Standby, then move the cursor to File at the top of the screen, hold down the MB and drag to the Quit with VT off. Go to the Console AIR window and turn N2 off. Also turn off the valve on the N2 tank.
When you have completed high temperature work, go to the VT window and toggle to VT Standby. Move the cursor to File at the top of the screen, hold down the MB and drag to the Quit with VT OFF.