A Hitachi table radio, solid state, uses transistors. Not a portable, so by some definitions it's not a "transistor". In any event, got it at a garage sale, as not working. It's a "hot chassis" design, the audio output transistor is a high voltage one, and the rest of the circuits are conventional low voltage transistor circuits. As seen in many such radios, it uses a dropping power resistor in series with the rectifier diode. In this radio, that power resistor went bad apparently on its own. Replaced it, radio now works. But I relocated this resistor away from the "high" side of the powerline, to the "low" side (connected directly to the radio's B- line and the power switch (which switches the low side of the line)). Keeps a hot resistor away from the filter cap.
And the radio doesn't seem to notice that its "ground" is bouncing at a complex 60Hz wave above external ground.
06-28-2015, 04:42 PM
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