AM/FM mono radio information

[wa2ise]

Originally Posted by Tom Bavis

Gee... I have that radio, and I DON'T have a schematic... I did use the Aux input with a CD player, assuming that it had an power transformer inside...but that turns out to be for heaters only, the B+ comes right off the AC line.

Usually such sets had a capacitor that coupled the ground of the aux input jack to the set's internal ground. Usually 0.1uF, sized to pass low frequencies reasonably well in a high impedance circuit, but to limit shocking current if a user gets between the aux jack ground and an external grounded item (and the set's internal ground happens to be connected to the hot side of the powerline).