In 1948, it was estimated that there were 150 million radios in use in the United States. The industry that kept these sets functioning was booming, especially since parts as well as new radios had been difficult or impossible to obtain during the war years. Thousands of radio repair shops existed across the American landscape, some operated by large national concerns such as RCA Service Company and Zenith, but many repair shops operated as privately owned, often "mon and pop" concerns. Radios of that era, whether large consoles or small portable or table radios, were hand-wired and therefore easily repairable either in the customer's home or in the service shop. Like physicians of that era, Radio and TV technicians still made "house calls." to service large consoles and early television sets. The radio repair business, and the early television repair ss as well, were lucrative for technicians and shops well into the 1960s.

A combination of high wage, insurance and mobility costs for shop owners, coupled with increasing difficulty in repairing cheaply made foreign equipment, along with difficulty in obtaining and stocking parts, are the main factors that destroyed the home electronics service industry by the 1980s.

The Museum Of Yesterday salutes the radio technician of old. Armed with nothing but SAMS Photofacts primitive test equipment, and their own gained experience, these technical gurus kept America's radios playing for more than half a century. In this gallery, we will visit some of the instruments that were considered essential in the repair shops of old.

This image is typical of radio service shops of the 1950s. Service technicians were called on to work on numerous brands and types of equipment, from radios, phonographs, televisions as well as other electronic devices. The technician had to be resourceful and familiar with the "bugs" that could affect the operatoin of each brand of set.

Most radio service technicians in the 20th Century were trained either in military branches, or in trade or technical schools. Various schools existed in localities around the country, but the most noted school was a correspondence school based in Washington, D.C. The National Radio Institute began in 1914, and at the height of its existence boasted 80,000 students. The school drew most of its students through ads in popular scientific magazines such as Popular Mechanics, Popular Science, Boys' Life and Popular Electronics. The ad below was typical of the school's advertising material from the era around World War II. For more history on NRI,

Rear view of the RCA Chanalyst chassis

The Chanalyst is an all around service bench instrument that was extremely popular because of it's inclusion of several test instruments in the same case. The instrument functioned as a signal generator, tracer and volt ohm meter. In addition, it could function as an AM receiver on steroids.

Below is a catalog cut on the Chanalyst from the 1946 Allied Radio Catalog. It was a pricey but desirable fixture in those days.

Throughout most of radio's "Golden Years," construction and servicing of sets usually involved the use of existing tools designed for electrical construction work such as the American Beauty soldering iron shown above. Heavy steel chassis, large gauge copper wire and bus bars, and large components such as transformers and coils, required sufficient heat to insure good solder connections. It was not until the end of World-War II that the Weller soldering gun was introduced, giving radio technicians an alternative to the use of large irons such as the one shown above.

Solder was also a separate component from the rosin flux cleaner that was needed to assist in the process. A typical soldering operation required dipping the iron into the soldering paste container, and then applying solder to the connection. With the advent of "core" solders, the rosin flux became an integral part of the solder wire, allowing both solder and flux to be applied in one operation.

With the advent of printed circuitry and micro-electronics in the late 1950s, new forms of soldering tools came on the scene. The "pencil" iron, along with electronic heat controls for critical soldering of small components, became the norm in the service business.

The SOLAR model CE capacitor checker was one of the often utilized instruments at the DeMajo Electronics Laboratory in New Orleans during the mid-20th Century era. After many years of searching, the museum was recently able to locate a Model CE for our permanent collection. You can view the manual for the Solar CE by clicking the button below.

What are the various types of tube testers, and what are the differesncs?

Tube testers come in a variety of styles and functionality. Generally the three main categories are those that only test filament continuity, emission checkers and mutual transconductance testers, The most thorough test can only be done with a mutual transconductance tester.

Aside from the filament only tester, which is usually made up of a neon bulb and resistor that are placed in series with the tube filament, the most common type is the Emission checker. These instruments place the tube into a circuit where plate voltage is applied to the tube, and a meter then reads the amount of current that flows through the tube with a suggested grid bias. If the tube is weak, fewer electrons will boil off of the cathode, so the meter will indicate insufficient current flow and therefore a weak tube. Most emission checkers also have the ability to detect shorts and noisy or loose elements, and some can even check continuity or capacitors.

The mutual transconductance tester is a much more complex instrument that not only places the subject tube into a working circuit, but these instruments can also simulate various conditions to which a tube might be subjected in specific applications such as audio processing, RF generation or amplification, and other special purposes. They are much more complex to operate, and usually are considerably more expensive than emission testers.