Summary

A triode, manufactured by Northern Manufacturing Company with brand name Marathon, introduced in about 1928. It was used as a replacemnt in all the tubes in a battery powered radio to allow the radoi valves to be heated by AC from a small transformer. Early valves were directly heated requiring DC on their filaments.

This Marathon tubes was sold with a Marathon AC kit, consisting of a cable with the necessary clips to connect the heater terminals to side of the tube base (cable is missing).

The AC kit eleminated the nedd for the messy and inconveneient filament battery associated with radios in the early 1920s. The battery was usually lead acid.

It used a 5.5 Volt indirectly heated cathode, consuming 1 Amp. The amplification factor was 7.3,

Physical Description

4 pin base with heater straps.

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