Repair manual

2-60
THEORY OF OPERATION
2. Cathode Ray Tube
a. Components
The Cathode Ray Tube (Figure 2-6) used in the Digital Palette is a
3-inch rectangular tube. It consists of:
o White Phosphorous-Coated Display Screen
o Three-Grid Electron Gun
Grid 1 - Brightness (Pin 1)
Grid 2 - Accelerator (Pin 6)
Grid 3 - Focus (Pin 7)
o Cathode (Pin 2)
o Heater (Pins 3 and 4)
o Anode
b. Functional Description
When the CRT is turned on, its electron flow increases. The electron flow
forms a stream that is attracted by the electron gun. Its three grids per
form several functions. They focus the stream into a sharp beam,
accelerating the electrons to a very high speed.
The acceleration is accomplished because of a positive voltage that is
applied to the accelerator grid of the electron gun. The positive voltage
has an attraction for the electrons which are negatively charged.
Figure 2-6. Cathode Ray Tube
Glass Envelope
Face Plate
Anode
Cathode
Electron Gun
(Grid 1-3)
Yoke
Inner Phosphor
Coating