>14 May 1997, Wednesday, 0910 EDT
>
>Dear Spinlanders,
>
> We are experiencing an instability problem with the VT unit attached
>to our Bruker AC-200 NMR system. A proton lineshape test on 10% CHCl3 in
>acetone-d6 results in a temperature shifted multiple of peaks, ranging from
>two to four peaks, for the four pulse experiment. The maximum observed shift
>is about 0.7 Hz. When the air compressor is turned off, much of the problem
>goes away. The magnet sits on compressed air supports.
> The above suggests that a regulator in the compressed air system is
>malfunctioning. Just wondering if anyone else has had a similar experience,
>and, if so, has a solution.
> As always, any useful responses will be collected and posted back to
>the groups.
> ***********************
Dear Lawrence,
Most of AC-spectrometers are equipped with B-VT1000 ~ ER 4111 VT
temperature controller. Please, look for the "Instruction Manual" and open
page "VT unit, Security ampli". Find capacity C11 in the scheme and read
nominal: 47 microFarades. After that open controller and you can see that
only 4.7 uF capacity is installed. We have changed this C11 capacity to
27 uF and have no problems with temperature stability now.
With best wishes and kind regards, Yuri Strelenko.
-- ********************************************************************* | Dr. Yuri A. Strelenko | | | N.D.Zelinsky Institute | Fax (7-095) 135 5328 | | of Organic Chemistry, | Tel (7-095) 135 9094 | | Leninsky prospect 47, | e-mail strel@nmr.ioc.ac.ru | | 117913 Moscow B-334, | | | Russia | | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^