[3DEM] Jamming of FEI low-noise film holders

[Norm Olson]

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3DEM'ers:  At the risk of just adding a "Me too"  we have also 
experience plate jams.  We haven't however shot enough film to 
thoroughly test the problem.  It seems, though with us, that it 
usually happens with the last plate in the cassette.  I have a 
project on the TO DO list that will be shot on film.  That should 
give me a good test run and let me know if we need to contact our 
service engineer.

Norm





At 11:53 AM -0400 7/10/07, John Rubinstein, U of T wrote:
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>
>Dear 3DEM list users,
>
>With our new FEI F20 microscope we selected low-noise film holders 
>for our plate camera system.  These holders do not have a metal back 
>and consequently do not produce backscattered electrons that can fog 
>the film (this topic has been discussed previously on the 3DEM 
>mailing list).  The advantage of these holders seems well 
>established at 300 keV but I have not seen measurements of film 
>fogging by backscattered electrons at 200 keV.  Thinking there was 
>no disadvantage in using these film holders, I selected them for our 
>200 keV instrument.  There was some delay in getting the low-noise 
>film holders and in the meantime we borrowed conventional holders 
>and cassettes without incident.
>
>When we started using the low-noise film holders, we ran into some problems:
>
>1) The low-noise film holders require different camera cassettes 
>(with springs set for the weight of the film holders).  While the 
>old FEI camera cassettes dropped right into position to engage film 
>inserting rod, the new cassettes are a much more snug fit and needed 
>to be pushed down into the microscope to engage the connection. 
>This difference led to a couple of plate jams before we learned that 
>the cassettes need to be pushed firmly into the microscope.
>
>2) Film holders occasionally jam in the top half of the cassette (in 
>our local terminology, the 'donator' part of the cassette).  As the 
>stack of plates is lowered (by gravity) during a session on the 
>microscope, one plate will occasionally jam in the donator and all 
>subsequent 'exposures' are taken without film.  Our engineer has 
>looked at the cassette and can not see why these jams occur.
>
>Has anybody else experienced this second problem?  Has anybody 
>determined the reason why these jams occur or found a solution for 
>it?
>
>Any information would be greatly appreciated.
>
>Best regards,
>John
>
>
>--
>John Rubinstein
>Molecular Structure and Function Program
>The Hospital for Sick Children
>555 University Avenue, Rm. 3330
>Toronto, ON
>Canada
>M5G 1X8
>Tel: (+001) 416-813-7255
>Fax: (+001) 416-813-5022
>www.sickkids.ca
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-- 



______________________________________________________________
Norm Olson
Cryoelectron Microscopy Facilities Manager
1510 Bonner Hall
Department of Chemistry & Biochemistry, MC-0378
University of California San Diego
La Jolla, CA 92093-0378
nholson at ucsd.edu
http://cryoem.ucsd.edu
Cell:  (858)220-2183
(858)822-6718 - Office; (858)534-5846 - Fax
______________________________________________________________
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