TV Trouble Quiz
July 1966 Popular Electronics

July 1966 Popular Electronics Table of Contents Wax nostalgic about and learn from the history of early electronics. See articles from Popular Electronics, published October 1954 - April 1985. All copyrights are hereby acknowledged.

Very few people these days would have any clue as to the causes of the CRT-type TV picture problems shown here - I certainly don't, even after looking at the answers (except for #4, which is pretty obvious given the choices offered). What I can claim is to have likely seen each one of those types of issues with all the cheap TV sets I've owned (especially #9). My current 26" LCD television (I only own one TV), which is ten years old this year, is still working fine and never displays any of those funny patterns. In the days of the Macs TV Service Shop stories, survival in the business depended on technicians being able to quickly diagnose and repair televisions and radios based on knowledge learned while attending the school of hard knocks. Of course success at servicing modern equipment sometimes requires extraordinary measures, but built-in test and diagnosis is part of many electronic systems today. Even your car has an OBD port for plugging a computer into to get a readout of hundreds of parameters and potential problem causes.

TV Trouble Quiz

By Robert P. Balin

To be successful in TV servicing, you must be able to interpret the various trouble symptoms that show up on the TV screen. Test your skill by matching the common troubles illustrated below (1-12) with their listed remedies (A-L).

A) Adjust deflection yoke or ion trap.

B) Replace phase detector.

C) Adjust automatic frequency control (AFC).

D) Replace horizontal output tube.

E) Adjust height control.

F) Replace vertical oscillator/amplifier.

G) Replace deflection yoke.

H) Check horizontal output tube for Barkhausen oscillation.

I) Replace low-voltage rectifier.

J) Check tubes in video circuits for filament-to-cathode short.

K) Replace sync separator/amplifier.

L) Replace r.f. amplifier in tuner.

TV Trouble Quiz Answers

1 - G) This keystoning effect may be the result of a short in the horizontal winding of the deflection yoke, or a short in the balancing capacitor across the winding.

2 - C) Slanting bars that change in number, width, and slant angle as the a.f.c. coil is adjusted are the result of the horizontal oscillator operating off frequency.

3 - A) Neck shadows are produced by the deflection yoke being positioned too far back on the neck of the tube. They are also produced by an incorrectly positioned focus coil or ion trap.

4 - F) A horizontal line across the face of the picture tube is an indication of no vertical deflection. This may be caused by failure of the vertical oscillator/amplifier tube, vertical output transformer, or other components in the vertical section.

5 - K) When the picture wobbles from side to side while rolling slowly from top to bottom, the indication is a loss of synchronizing pulses. This is usually caused by a defective sync clipper or sync amplifier tube, or failure of some other sync component.

6 - J) This dark bar is produced by 60-cycle hum in the video signal. It usually results from a filament-to-cathode short in one of the i.f., r.f., or video amplifier tubes.

7 - E) Elongation of the bottom portion of the picture is usually caused by an improperly adjusted height (size) control. This control also has a slight effect on the top portion of the picture during adjustment.

8 - I) A picture having insufficient height and width (and usually poor brightness, focus, and sync) is usually caused by low B+ voltage. Try a new low-voltage rectifier.

9 - L) A weak r.f. amplifier tube, as well as a poor antenna, will usually produce an abundance of snow in addition to a weak, washed-out picture.

10 - D) A picture which fills out completely at top and bottom, but which shrinks at the sides, can be traced to a weak horizontal output tube. Low line voltage - during peak evening hours - can also cause a similar effect.

11 - H) Beadlike, black vertical lines on the left-hand side of the picture tube are usually due to what is generally known as Barkhausen oscillation, which takes place in the horizontal output tube. Sometimes, mounting a small magnet on the tube will cure this condition.

12 - B) Loss of horizontal sync, as evidenced by this split image, can be caused by an incorrect phase relationship between the horizontal sync pulses and the horizontal oscillator output. Try changing the phase detector.

Posted April 20, 2018

Popular Electronics published many quizzes over the years - some really simple and others not so simple. Robert Balin created many of the quizzes. This is a listing of all I have posted thus far.