Re: General Capacitor Question
I've attached a photo of an early Zenith transistor radio. Some electrolytics were on the pcb, others not. They had ceramic bodies. Often they are completely O/C and dried out, especially the ones that filter the AGC circuit. Its worth re-building these capacitors.
Oddly, there is a "classic mistake" in many transistor radios, the AGC capacitor really needs to be a bipolar type. With no signal it usually has a small amount of the correct polarity voltage applied, but with a strong signal it reverses. So in many transistor radios, especially very old ones the AGC filter cap spends most of its life with reverse polarity applied, fails first, and the IF goes unstable. It amazed me that very few manufacturers of transistor radios recognized this and the defect was under everyone's noses for decades and ignored. Some radios had the polarity of the capacitor flipped, so most of the time , on station, the applied voltage polarity was correct.
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