[3DEM] F30 cartridge problem

[Bob Grassucci]

Hi Bill,
         Be aware that the threaded plastic rod that holds the cartridge 
thermally in contact with the stage mating surface is plastic and 
eventually may become cross threaded or worn over time.  This happened to 
us and the threaded plastic rod would no longer pull the cartridge into 
position.  This resulted in the cartridge staying attached to the insertion 
rod instead of being released in the column.  That requires a service call.
         Regards,
         Bob

At 11:14 AM 10/14/2004 -0700, you wrote:
>On Oct 14, 2004, at 6:15 AM, Bob Grassucci wrote:
>
>>         This sticking of the cartridge may be from contamination 
>> residing on either the inner conical surface of the stage or the outer 
>> conical surface of the cartridge that is acting like a glue.  The warm 
>> surface of the cartridge (or the pressure between the surfaces) would 
>> melt it and after it cools down it will again solidify.  Is there a 
>> significant amount of contamination building up on your sample if you 
>> leave it in for overnight?  One thing to try is to use the plastic screw 
>> rod to break the bond between the cartridge and specimen stage by 
>> pushing into the cartridge a few times (without turning).  I have also 
>> sent this to the tecnai user list in case there are any other Polara 
>> owners experiencing this problem there.  Another potential reason could 
>> be the position of the plastic screw rod into the cartridge.  There is 
>> the possibility that the plastic rod is not becoming fully disengaged 
>> from the cartridge.  There must be sufficient displacement of this rod 
>> so that it is fully removed.
>>There is a spring that should push the plastic rod out of the stage once 
>>it is disengaged.  Please contact me if you have any further 
>>questions.  Good luck.
>Hi Bob,
>         We also considered contamination--especially since we thought at 
> first that the problem only occurred after inserting a room temp cartridge.
>We have not seen any contamination on any of the cartridges nor any 
>increase in contamination rate; however, we have not inspected the stage, 
>so we cannot say that there is no problem there.  On the other hand, 
>inserting a sample that is at ~-170 C into a stage that is at ~-190 C and 
>having the 20 degree temperature difference cause melting and re-freezing 
>limits what the purported contaminant could be (I'm pretty sure that there 
>is no ethane in the column, but I suppose it's possible).  Your suggestion 
>about pushing with the screw is excellent, and I'm going to try it next 
>time the problem occurs.  That will really be a help if the sticking 
>occurs between the first and second tilt series in a dual-axis data 
>set.  I'm pretty sure that the screw is being completely disengaged; the 
>knob comes all the way out and acts like it is free.  Jos Peeters is 
>coming next week to look into this, and I'll post anything he finds out to 
>the Tecnai users list (I don't have the particulars about that list, but 
>one of my colleagues can direct me to it).
>                                                 Yours,
>                                                 Bill

********************************
Robert Grassucci
Howard Hughes Medical Institute
Wadsworth Center
Empire State Plaza
Albany, NY 12201-0509

bobg at wadsworth.org
Phone: (518)474-5821
Fax:	(518)486-2191