COLOUR TELEVISION DISPLAY TUBES
• The colour television picture tube screen is
coated with three different phosphors, one for
each of the chosen red, green and blue
primaries.
• The three phosphors are physically separate
from one another and each is energized by an
electron beam of intensity that is proportional
to the respective colour voltage reproduced in
the television receiver.
Akshay Jilowa
G.P.C.G. Jalandhar
2
COLOUR TELEVISION DISPLAY TUBES
• The object is to produce three coincident
raster with produce the red, green and blue
contents of the transmitted picture.
• While seeing from a normal viewing distance
the eye integrates the three colour
information to convey the sensation of the
hue at each part of the picture.
Akshay Jilowa
G.P.C.G. Jalandhar
3
COLOUR TELEVISION DISPLAY TUBES
• Based on the gun configuration and the
manner in which phosphors are arranged on
the screen, three different types of colour
picture tubes have been developed.
These are:• 1. Delta-gun
• 2. Guns-in-line or Precision-in-line (P-I-L)
• 3. Trintron Colour
Akshay Jilowa
G.P.C.G. Jalandhar
4
Delta-gun colour picture tube
(a) guns viewed from the base (b) electron beams, shadow mask and dot-triad
phosphor screen (c) showing application of ‘Y’ and colour difference signals
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between the cathodes and control grids
DELTA-GUN COLOR PICTURE TUBE
• This tube was developed by Radio Corporation on
America (R.C.A). It employs three separate guns on
for each phosphor. The guns are equally spaced at
120 degree interval with respect to each other and
tilted inwards in relation to the axis of the tube. They
form an equilateral triangular configuration.
Drawbacks of the Delta-gun Tube
• Convergence is difficult and involves considerable
circuit complexity and service adjustments. In
most delta-gun tubes, four static convergence
magnets and a dynamic convergence assembly
are employed.
• The focus cannot be sharp over the entire screen
because the focus and convergence planes
cannot remain coincident for the three beams
which emanate from guns positioned at 120°
with respect to each other around the tube axis.
• The electron transparency of the mask is very low
since it intercepts over 80 percent of the beam
currents.
Akshay Jilowa
G.P.C.G. Jalandhar
7