All American Five
The term All American Five (abbreviated AA5) is a colloquial name for mass-produced, superheterodyne radio receivers that used five vacuum tubes in their design.
These radio sets were designed to receive amplitude modulation (AM) broadcasts in the medium wave band, and were manufactured in the United States from the mid-1930s until the early 1960s.
[1][2] By eliminating a power transformer, cost of the units was kept low; the same principle was later applied to television receivers.
Transformerless designs had a metal chassis connected to one side of the power line, which was a dangerous electric shock hazard and required a thoroughly insulated cabinet.
At least one radio manufacturer, Arthur Atwater Kent, preferred to go out of business rather than attempt to compete with 'midget' or low-cost AA5 designs.
If the dial lamp failed, that part of the rectifier heater would have a larger current which could burn out the tube in a few months.
The frequency mixer was of the pentagrid converter design to save the cost of a separate oscillator tube.
Ventilation holes could be large enough to allow children to poke their fingers, or metal objects, through.
The hazard was eliminated from later sets by the use of an internal ground bus connected to the chassis by an isolation network.
[7][8] Over the years, these paper capacitors often become leaky, and could allow sufficient current flow to give the user a shock.
Because areas near Niagara Falls had 25 Hz power, some Canadian sets had slightly larger filter capacitors.
[1] In the postwar period, some makers built sets with a mixture of miniature, octal, and loctal types.
[10] Sometimes only the tube heater power was derived from a windmill, and dry batteries were retained for the plate voltage supply.
According to various editions of the RCA Receiving Tube Manual, the heater string of an AC/DC radio should be arranged in a particular order to minimize hum.
Assuming that all functions are performed by separate tubes, the heaters in the string should be arranged as follows: Not all manufacturers followed this recommendation.
Many black-and-white and color television receivers were built using All American Five principles, including a hot chassis and series-wired heaters.
The designs were found primarily in portable or inexpensive sets ranging from the 1950s to even as late as the GE Portacolor series which was finally discontinued in the 1980s.
Since the chassis of the set may be connected directly to the live side of the power line, service shops used an isolation transformer to protect technicians from a shock hazard.
