After the vacuum has been released screw the bleed valve back into the tube housing. Remove the four Phillips head screws on the front lid that covers the cathode assembly and carefully remove. Let the cover drop down to expose the filament lead wires. Unscrew the allen head screws holding the filament lead wires to the filament terminals that are protruding from the bottom of the cathode assembly. Be careful not to completely remove the screw from the filament lead wires, and keep the wires straight as they are unscrewed from the filament terminals, by pulling the filament lead wire towards you with the needle nose pliers.
Fingerprints can adversely affect the vacuum, so use extreme care.
Unscrew the two captive screws at the bottom of the cathode and remove the cathode from the tube housing. Do not completely remove the allen head screws from the cathode. Place the cathode with the filament facing down on a clean working surface. Remove the two large Phillips head screws on the back of the cathode and remove the back of the cathode assembly. Carefully clean the inside of the cathode with a lint free cloth and use canned air to blow any residual lint or dust off the cathode.