[WISCOJIM]

Originally Posted by LADR

This thing uses 9 and 13.5 volt batteries for some reason.

The reason why GE had decided to use two separate battery line voltage supplies in its original 1955 design, is that the -4.5 volts was used "only" for the 2N137 1st I.F. PNP transistor emitter "fixed" bias voltage supply and was also used for the radio's AGC (Automatic Gain Control) action. GE had used the -13.5 volts for the rest of the circuitry, including the "self" bias voltage supply from resistors (R12-2700 ohms + R5-2700 ohms + R4-220K ohms) for the base of the 2N137 1st I.F. PNP transistor. And when the radio's circuitry would receive a strong radio signal, the 2N44 audio output PNP transistor will conduct more current flow and thus there would be a greater voltage drop across the supply resistors for the base of the 2N137 1st I.F. PNP transistor. This will cause the base voltage to be less negative, while the separate -4.5 "fixed" bias voltage for the emitter of the 2N137 1st I.F. PNP transistor, will remain more constant. This AGC action will cause the "forward" bias of the base and emitter junctions of the 2N137 1st I.F. PNP transistor to be lowered and thus reducing the Beta (hFE) gain of this transistor, which will lower the overall radio's audio volume output.

Lots more info on this radio here (thanks to Rich Hirsh & ARF): http://antiqueradios.com/forums/view...p?f=4&t=208340

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