Ts4d Motorola

[jr_tech]

Originally Posted by timmy

It blanked out all as if no speaker was connected, or as if it were turned off. If the hum was gone there should have been other noise like a hiss when no antenna connected.

Since that is the last audio stage, there would not be much/any hiss when it's input (the grid) is grounded.

Another experiment... instead of grounding the disconnected grid, insert a 470 k ( or so ) resistor between the grid and either end (try both) of the 330 ohm cathode resistor.

jr