Microscope Schedule
Logbook
NYSBC Intranet
NYSBC Contacts
Cryo-EM home

NYSBC home
NMR Facility
X-Ray Facility
Protein Production Facility
Electron Crystallography Center

Cryo-EM Site map

Filament Exchange

Determining if the filament is blown

• You had a beam, but now you do not.
  • You did not move the sample
  • or change any microscope parameters
• The Beam Current value drops to the filament off value

Removing filament

• Remove sample
• Press Gun Vent button - control panel
• Flip Gun Lift switch to on - control panel
• Wait for gun to lift (patience)
• Put on lint free gloves
• Unscrew outer ring from wehnelt assembly
• Pull out wehnelt assembly
• Replace the outer ring into the gun
• Make sure the o-ring is clean and properly aligned
• Flip Gun Lift switch to off - control panel
• Wait for gun to lower (patience)
• Press Gun Vent button - control panel

Examine filament for damage

• Wear lint free gloves when handling gun parts
• Unscrew the wehnelt cap from the wehnelt assembly
• Using a stereo microscope observe the filament for damage and determine its cause

Cleaning Whenelt Cap

• You will need
  • Aluminum Foil
  • Pol polish
  • Mr. Clean (ammonia free)
  • 4 - 250 mL beakers
  • Cotton tipped applicators
  • Ethanol (reagent grade and 200 proof)
  • Lint free cloth

• Wear lint free gloves when handling gun parts
• Use a cotton tipped applicator and pol polish to clean the contamination from the wehnelt opening
• Only a small amount of pol polish is necessiary
• Prevent the pol polish from contaminating the threads
• Polish until all of the visual contamination is gone
  • Continual additions of pol polish will always result in dirty looking resudue on cotton applicator
• Remove all visible pol polish witht he cotton applicator

• Begin sonication steps (each step is a miniumum of 5 minutes)
  • first sonication - Mr. Clean and water
  • second sonication - DI water
  • third sonication - reagent ethanol
  • fourth sonication - 200 proof ethanol
• Dry with a lint free cloth

• If you have the luxury of time
  • Place the Whenelt cap in 100% Micro-90 overnight
  • This eliminates the Pol polish step

Centering the filament

• Wear lint free gloves when handling gun parts
• Filaments for the 1230 are precentered at the factory
• Screw on wehnelt cap and remove old filament
• Observe the new filament under the stereo microscope for defects
• Insert new filament using guide pins for orientation
• The following steps are best carried out under a stereo micrscope
• Make sure the filament is centered with in the wehnelt opening
• Screw the wehnelt down until the tip of the filament is flush with the whenelt opening
• Retract the filament tip with two full turns of the whenelt cap
  • Each full turn onthe wehnelt cap is equal to 0.5mm
  • Double check your work by making sure the filament tip disappears when tilted to a 45 degree angle

Replace the wehnelt assembly into the microscope

• Press Gun Vent button - control panel
• Flip Gun Lift switch to on - control panel
• Wait for gun to lift (patience)
• Put on lint free gloves
• Unscrew outer ring from wehnelt assembly
• Push in wehnelt assembly using the guide pins for orientation
• Replace the outer ring into the gun
• Make sure the o-ring is clean and properly aligned
• Flip Gun Lift switch to off - control panel
• Wait for gun to lower (patience)
• Press Gun Vent button - control panel

Essential aligments after filament replacement

• Gun shift center beam at crossover
• CL Stig in setup menu/F1/F2
  • Desaturate filament
  • Make filament shadow symetrical
• Gun tilt

-- KdDerr - 27 Jul 2007