All,
We're having a problem with the inner glass insert of our Nalorac MDG400B 3-mm dual microprobe repeatedly breaking. This is happening on a monthly basis. I don't think it's user abuse...in six years of use of the instrument ('96 DRX400), not a single NMR tube has been broken in a probe. To me, it does sound like the tubes are landing hard. We haven't had the problem with our Bruker 5-mm QNP probe, and tube landing sounds normal. We've tried suggestions from Bruker: Air flow from the console > 4 bar; increasing the lift offset significantly; and ensuring that the O-rings on the upper shim stack are present. Suggestions from Varian's probe repair were to make sure lift air was high enough, and to not use cheap tubes (we use Wilmad 328s exclusively). Inserts are still breaking.
We'd really like to continue using the probe, are out of ideas, and certainly cannot justify a monthly repair expense of $1000-1500. I'd greatly appreciate any suggestions, regardless of how obvious they are. Thanks in advance.
John
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John Carney, Ph.D.
Analytical Chemistry
Kosan Biosciences, Inc.
3832 Bay Center Place
Hayward, CA 94545
phone: (510) 731-5217 (office)
(510) 731-5324 (lab)
fax: (510) 732-8401
www.kosan.com
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Received on Thu Oct 20 2005 - 17:06:50 MST