If you are in the CRT TV and Monitor repair line, I’m sure you had come across picture tubes that were dim and weak. Some of you may have the CRT restorer or the rejuvenator to restore dim picture tube. Do you know that not all CRT tube can be restored? Yes, this is most probably due the getter inside the tube had been used up fully. The function of the getter is to “degassed” stray air or gas inside the tube. The getter in most glass tubes is a small cup or holder, containing a bit of a metal that reacts with oxygen strongly and absorbs it.
The getter material is made of barium which oxidizes VERY easily when it is pure. When the tube is pumped out and sealed, the last step in processing is to “fire” the getter with an induction heater, producing a “getter flash” inside the tube envelope. That is the silvery patch you see on the inside of a glass tube. By activating the getter, it is a guarantee that the tube has good vacuum. A good vacuum tube will usually preserve the long life of cathodes in the CRT
