Hello Chris,

We have had a similar problem with our MultiPrep. The external cold 
finger could not stabilise its temperature. The reason was that the 
cement holding the thermocouple inside the cold finger was damaged. In 
fact when we looked at it carefully it looked as if it had been 
"vaporised" on the insulation mat underneath and the thermocouple was 
almost completely loose. Once this cement is damaged or even just 
cracked you can get a lot of moisture inside the thermocouple hole and 
the temperature readings become erratic.
As we had a backlog of analyses and wanted to carry on the measurements 
until we recieve a replacement cold finger and we took a desperate step 
and put the thermocouple back in position using some epoxy resin 
(araldite is the brand name)we had in the lab. We were not optimistic 
that it would hold very long but our cold finger has been working fine 
like that for about a year now.
Hope this helps.
Good luck,


-- 
François FOUREL

UMR CNRS 5125 PEPS
Université Claude Bernard Lyon 1
2 rue Raphaël Dubois - Bât. Géode
F-69622 VILLEURBANNE Cedex - FRANCE

Tél : +33 (0) 4 72 44 62 42
FAX : +33 (0) 4 72 43 16 88
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Chris Yarnes a écrit :
> Hi,
> 
> Has anyone else had problems with the coldfinger LN2 supply lines on the 
> MultiPrep?  During a batch of carbonates, after a couple samples the 
> analysis stalls and logs: "unable to maintain external C/F temp".  We 
> believe it to be in the supply lines since we have some pipe insulation 
> of questionable quality and see visible freezing in the lines (we are 
> currently pursuing this avenue), but perhaps its in the coldfinger 
> itself?  Never had this problem, so any advice on how to troubleshoot 
> this would be most appreciated.  btw, the thermocouple should be fine, 
> it was replaced last winter.
> 
> Thanks in advance,
> 
> Chris
>