CRT Problems was:(no subject)

From: John Lawson <jpl15_at_panix.com>
Date: Wed Dec 13 00:30:33 2000

 If the 'burn mark' on the inside of the neck of the tube is silvery-edged
and/or mettallic looking, then it is possible that is the residue of the
"getter" flash. To sweep out the last of the reactive gas molecules that
are left in a vacuum tube (mostly dissolved in the surfaces of the
elements) a small amount of a compound called a getter is caused to burn
inside the tube after evacuation. This absorbs the last bits of gas in the
device and deposits them on the side of the neck.

  Note that if this 'getter spot' is grey or has flakey edges (not
silvery) then your CRT is most likely gassy and needs to be sent to
Picture Tube Heaven.


  On the other front, if the heater is 'arcing' in the tube, this could
mean that it is actually open and not making contact all the time, or that
there is a short between the heater element and the cathode
structure... both of which scenarios bode ill for your Tube. The picture
disturbances that you report sound like loss-of-emission symptoms that I
would expect to see if the heater/filament is intermittent.


  One last Thought: there used to be a quite common little gizmo called a
CRT Rejuvenator... basically it hit the heater/cathode parts with a
momentary elevated voltage to burn away shorts and attempt to re-weld open
heater filaments. You might try this, but it's a Last Resort type of
thing and seldom (if ever) permanent.



  Cheerz

John
Received on Wed Dec 13 2000 - 00:30:33 GMT