Hi Mary,
I think the biggest issue is "the possibility of long term contamination".
Running the coldhead longer than recommended before replacing it carries the
risk that somehow the system may get contaminated. It is not clear what that
means exactly, but it can happen to either a Varian or Bruker system.
Removing the contamination if it happens is tricky and also expensive.
I would strongly recommend the cryoprobe service contract. I am not a fan of
console service contracts, but I think the cryo one is money well spent. One
probe failure plus the annual coldhead service can easily exceed the price
of the contract.
I think that the 7700-CS system is now superior to the Bruker one. From what
I know it is more robust, and less likely to fail.
Good luck,
Greg
-----------------------------------------------------------------
Gregory J. Heffron
Director, Harvard Medical School NMR Facility
Harvard Medical School
240 Longwood Ave.
Boston, MA 02115
Phone: 617-432-1812
Fax: 617-432-4383
_____
From: Mary Howe [mailto:howe_at_chemistry.ucsc.edu]
Sent: Tuesday, June 23, 2009 5:48 PM
To: ammrl_at_ammrl.org
Cc: Jim Loo
Subject: AMMRL: Another Cold Probe survey
Another Survey:
The 600MHz Varian 7700-CS Cold Probe system on our Inova 600 has been
working for about a year. Among other factors, the 7700-CS Closed-Cycle
Cryogenic System boasts a new robust CryoBay.
We would like to get feedbacks from those who own the Varian 7700-CS Cold
Probe system (or Bruker equivalent). Do you have a Service Contract for
the whole cryo system or just the Cold Head? What problems are you
experiencing?
Our understanding is Cold Head maintenance (cleaning) implies complete Head
replacement. That being the case, why not just operate the system for 2
years or until the Head fails? It doesn't cost any more - we checked. And
if it hasn't failed after two years, then the Cold Head and the Oil Absorber
can be serviced at the same time. The down side of this scenario is the
Probe must be returned to Varian. Institutions that are able to absorb
being without the Cold Probe for a month or so could potentially save a
bunch of money. A full Service Contract costs about $30,000.00
dollars/year.
We will post summaries.
Mary Howe
NMR Facility
UCSC
Santa Cruz, CA
Received on Tue Jun 23 2009 - 16:41:32 MST