11-03-2023, 08:45 PM
The Philco 295 battery radio receiver was designed to perform as well as a mains radio. To achieve this the HT voltage is 160V. The push-pull output stage employs a Brimar type 2103, a very rare valve in the UK. https://www.radiomuseum.org/tubes/tube_2103.html
I got lucky finding the ex-Fisher-Sanyo video recorder mains transformer which has a display driver secondary of 55volts, this added to other windings and a voltage doubler realised an output of near 180volts. A TIP49 transistor is employed as the series regulator to supply the 160volts for the output valve.
The same transformer supplies through an LM317 the 2volt filament supply. Another winding is used for the grid bias which is -3volts for the audio amplifier and -9volts for the 2103 double pentode output valve. Another LM317 regulates the grid bias.
The screen grids of the 1A4E RF and IF tetrodes a supplied with 60volts derived from the main HT line.
Geordie McBoyne.
I got lucky finding the ex-Fisher-Sanyo video recorder mains transformer which has a display driver secondary of 55volts, this added to other windings and a voltage doubler realised an output of near 180volts. A TIP49 transistor is employed as the series regulator to supply the 160volts for the output valve.
The same transformer supplies through an LM317 the 2volt filament supply. Another winding is used for the grid bias which is -3volts for the audio amplifier and -9volts for the 2103 double pentode output valve. Another LM317 regulates the grid bias.
The screen grids of the 1A4E RF and IF tetrodes a supplied with 60volts derived from the main HT line.
Geordie McBoyne.
