Chapter 4: Picture Tubes

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This is the Chapter 4: Picture Tubes end chapter exercise in Basic Television – Grob TV as one of the Electronics Engineering topic. In Preparation for the ECE Board Exam make sure to expose yourself and familiarize in each and every questions compiled here taken from various sources including but not limited to past Board Exam Questions in Electronics Engineering field, Electronics Books, Journals and other Electronics References.

Start Grob TV End Chapter Exercise 04

Answers are Underlined

Chapter 4

Picture Tubes

4-1

a. What is the diagonal screen size for 19CP4 picture tube? 19
b. To what deflection angle does a maximum deflection angle of 45° either side of center correspond? 90°
c. The usual heater voltage for picture tubes is 6.3 V.

4-2

a. Typical anode voltage for a 25-in color picture tube is 30 kV.
b. Typical anode capacitance is 2000 pF.

4-3

a. The phosphor numbers for monochrome is P4 and for color picture tubes is P22.
b. Aluminized tubes do not need an ion-trap.
c. What is the color of the P1 phosphor? Green

4-4

a. Control Grid is the most negative electron gun.
b. Ultor or Anode is the most positive electron gun.
c. Most of the electrons in the beam flow out of the anode terminal.

4-5

a. The crossover point for focusing is formed by the first electron lens.
b. A G3 voltage of 200V is used for low-voltage focus method.
c. For most color picture tubes, the G3 focus voltage is an adjustable value of several kilovolts.

4-6

a. The small magnets embedded in the yoke housing correct for pincushion distortion.
b. The coils above and below the electron are for H scanning.
c. Two permanent-magnet rigs just behind the yoke are used for centering the beam in monochrome receivers.
d. Neck shadow result when the deflection yoke is too far back.

4-7

a. Separation of the beams for the red, green and blue colors is accomplished by the shadow mask.
b. In-line guns are easier than the delta guns in making the convergence adjustments.

4-8

a. A shadow mask has about 300,000 holes.
b. The holes in the shadow mask is conical in shape to prevent secondary emission.

4-9

a. Ambient room lighting makes black on the screen appear lighter.
b. Opaque phosphor masking improves contrast by making black appear darker.

4-10

a. A TV projection picture shows less detail than the image on a direct-view picture tube.
b. The typical anode voltage for projection tubes is 30 to 80 kV.

4-11

a. When a picture tube is being discharged, the ground end of the clip lead should be connected first.
b. Hold-down circuits limit the amount of color saturation.

4-12

a. Weak emission from the cathode of the electron gun causes saturation limiting, with the picture appearing silvery gray where it should appear white.
b. No picture, with a bright, blank raster and no control of brightness, may indicate a short circuit between the cathode and the control grid in the picture tube.
c. A yellowish brown monochrome picture slowly balancing to a neutral gray scale indicates weak emission in the blue gun.