a. These electrons are guided through the pickup tube by grids 1, 2, 3, and
4. These grids control magnitude, focus and acceleration of the electron beam on
its way to the target. If any of these grids are defective in any way, they will
cause focus problems or damage to the target.
b. These voltages and currents must be checked frequently for maximum tube
performance and life. Let's put the entire pickup tube operation in sequence and
see how it works:
(1) Power is applied to all required inputs.
(2) The heater heats the cathode and then emits electrons.
(3) Acceleration grids control the speed and magnitude of the electron
(4) The faceplate of the pickup tube is exposed to a light image: this
means it is conducting.
(5) The electron beam strikes the photoconductive portion of the pickup
tube, and a small amount of current is passed from the target to the
(6) The electron beam has traced the entire face of the pickup tube: at
this time, a sufficiently large amount of voltage (blanking) is applied to the
cathode during retrace. This blanking pulse will not allow the retrace line to be
NOTE: Remember, this is basically the operation of a
pickup tube. The pickup tube passes its electronic
information into the preamplification circuitry.
ALWAYS refer to the manufacturer's manual for
correct voltages and current applicable for your