Vintage battery Radio Power Pack

 

This unit will work for most 4 valve battery radios from the past. It utilizes components available to the modern builder. High voltage transformers with extra windings for valves and no longer made. But transformers for low voltage transistor circuits are common. This unit uses 2 x 20v secondary's, but a 15v type will also work well.

HT circuit

This uses a voltage multiplier arrangement x 4. Each diode will rectify 1/2 of the AC waveform and then discharge it across first capacitor and so on until 90 volts is achieved. Similar circuits were used in television receivers to generate EHT voltage for the CRT. Also used in neon high light voltage circuits. The output voltage is stabilized by C & R at the end of circuit.

LT Circuit

LT is stabilized by a modern i/c circuit arrangement known as a Buck Convertor, mainly made in China and can be found on-line for as little as 50p each. The LM2596 is supplied with all the components needed for it to work handling output current up to 2 amps, more than needed for most 1.5, 2, & 4 volt radio batteries. The chip operates at 40 megahertz and can create large amounts of radio interference. The answer is to install inside a small tobacco type tin that has been earthed. Make sure external holes are tiny as at that high frequency the signal will escape.

I've covered the mains terminals with cardboard to isolate from stray fingers.

The HT and LT circuits were made on Vero strip boards with pre drilled holes. Bridge diode can be any that can handle low voltage up to 3 amp current. Similar units sell on-line made in France around £60, but made by yourself can be done for as little as £20.