EF50 One Valve Radio Power Supply Using DC Adapter

When choosing a DC adapter "wall-wart" for the power supply, make sure it has a conventional transformer inside and is not the switched-mode type. The latter type does not work and the radio will pick up a huge amount of radio frequency interference. If you have the old-fashioned type with a conventional transformer, then it should be a robust one capable of delivering two amps or more, and a voltage greater than +12 V DC, and less than 15 V.

Since 0.3 A for the filament is a lot of current, even if one uses banks of batteries, they would deplete within hours. Batteries are also expensive and not environmentally friendly; therefore, the sensible and cost-effective option is to power it from the mains. If you already have a robust wall-wart type adapter that does not employ switched mode circuitry, and provides a few amps of current, then you can omit the bridge rectifier and transformer from the circuit. However, you will still require the voltage regulators to produce the 6 V and 9 V.

Wall-wart type adapters usually do not employ the earth pin; therefore, you will need to attach a separate earth wire to the negative rail of the one valve radio circuit.

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