TV X-Rays Are Back
June 1969 Radio-Electronics

June 1969 Radio-Electronics [Table of Contents] Wax nostalgic about and learn from the history of early electronics. See articles from Radio-Electronics, published 1930-1988. All copyrights hereby acknowledged.

Color television was a big hit with homeowners and was adopted fairly rapidly in the 1960s even considering the relatively high cost and low number of network color broadcasts in the beginning years. The enthusiasm underwent a severe reduction when word got out that large doses of x-rays were streaming out of the front of the cathode ray tube (CRT) for sets that did not take precautions to prevent it (which was the majority of sets initially). The major cause was extremely high voltages applied between the electron gun and phosphorescent raster grid - in the neighborhood of 35 kV or more - when the high voltage regulator circuit malfunctioned. Note that even when everything was working properly, a small amount of x-ray radiation was emitted. The x-ray problem received a lot of attention in the electronics trade magazines which targeted service technicians because of their higher than average close proximity exposure to energized CRTs. If a 25 kV zap didn't maim or kill them instantly, long-time exposure to x-rays might do the job at a slow rate. LCD and LED screens don't have that problem. See the "TV X-Rays" column in the subsequent April 1970 issue of Radio-Electronics.

See also How the Cathode-Ray Tube Works, Picture Tubes, TV X-Rays, TV X-Rays Are Back, and Whap - You're X-Rayed.

TV X-Rays Are Back

Suffolk County (Long Island), New York - A 14-month study of 5000 color sets conducted by the Suffolk County Health Department indicates that 20% of the sets were delivering excessive x-rays.

The study covered sets from 37 manufacturers, and at least one color receiver of each brand was found to be emitting radiation in excess of the danger level (0.5 milliroentgens an hour at a distance of two inches from the surface of the set).

The door-to-door survey was conducted by Seymour Becker, a physicist with the County Public Health Service.

Using these figures in an extrapolation, three million of the 15-million color sets now in use in the United States are emitting excessive x-rays.

Mr. Becker reports he found 15 separate causes for the excessive radiation, which was being emitted in all directions. Mr. Becker said that all x-ray emissions, even non-harmful ones "technically can be reduced to zero."

The amounts of radiation measured varied from 0.5 mR at 5 cm to as much as 150 mR. The average offender emitted 2 to 5 mR.

Power supply voltages in the malfunctioning sets ran as high as 40,000 volts with an average of 32,000 to 38,000. Normal high voltage is about 25,000 volts.

Editors Note: An excessive high voltage is almost always accompanied by x-ray emission we recommend all technicians to check the high voltage of every color set they service and make any needed repairs. To the set owner we urge that you look at your picture carefully. If it is out of focus or narrow (black edges at the right and left) have your set's high voltage checked immediately. The troubles just described are often produced by excessive high voltage. And excessive high voltage is often accompanied by excessive x-rays.

Color and Monochrome (B&W) Television Articles

• Color Television Has a Problem - May 1966 Radio-Electronics
• What You Want to Know About Television - February 1949 Popular Science
• Electronic Color Television Is Here - February 1947 Popular Science
• Television on the Job - February 1947 Popular Science
• What You Should Know About X-Ray Radiation in TV Sets - November 1967 Radio-Electronics
• Apollo 10 & 11 Color Video Camera Used Rotating Color Wheel - August 1969 Radio-Electronics
• What Happened at Oslo? - ITU Color TV - January 1967 Radio-Electronics
• Color Television Past Present Future - January 1954 Radio-Electronics
• Basic Color TV, Part I - January 1954 Radio-Electronics
• How Television Cathode Ray Tubes Are Made - July 1938 Radio News
• Color Television Fundamentals, Part 1 - March 1954 Radio & Television  News
• Color Television Systems - January 1951 Radio-Electronics
• Simulating a CBS Color Signal - September 1951 Radio & Television News
• The Strange World of Color Vision - January 1958 Radio Electronics
• Color Television? - December 1949 Radio & Television News
• Fundamentals of Color TV: The NTSC System - April 1954 Radio & Television News
• Color TV - October 1953 Radio & Television News
• The Color TV X-Ray Problem - November 1968 Radio-Electronics
• Introduction to Modern Television - February 1939 Radio News
• Television Industry Prepares for Postwar - January 1945 Radio News
• Television Transmission Lines - May 1952 Radio & Television News
• Television in Great Britain - January 1945 Radio News
• Television Set Shipments by Areas - May 1949 Radio & Television News
• Television Forges Ahead - March 1930 Radio News
• The Television Test Pattern - January 1949 Radio & Television News
• Television Tubes by the Thousands - December 1947 Radio News
• Television I.Q. Quiz - October 1948 Radio & Television News
• Television, As I See It - January 1945 Radio News
• The Outlook for Color TV - March 1957 Radio & Television News
• Color TV Today - September 1959 Popular Electronics
• Mac's Service Shop: Motorola's 1974 Color TV Receivers - November 1973 Popular Electronics
• Mac's Service Shop: Cost of Color TV Service - February 1969 Electronics World
• Practical Color TV for the Technician - September 1957 Radio & TV News
• Anxiety Amid Affluence: Why Color-TV Makers Worry - December 27, 1965 Electronics Magazine
• Fundamentals of Color TV - Tri-Gun Receiver Circuits - June 1954 Radio & Television News
• 3-D Color TV for the Future? - May 1958 Radio News
• Mac's Radio Service Shop: Barney Takes on Color - February 1955 Radio & Television News
• TV X-Rays - April 1970 Radio-Electronics
• TV X-Rays Are Back - June 1969 Radio-Electronics
• Television in Twelve Colors - October 1930 Radio-Craft
• Trinitron - Still a Mystery? - February 1972 Popular Electronics