I'm replacing a selenium rectifier with a diode and dropping resistor, and can't seem to connect my knowledge of 1N-4004 diode polarity with the schematic. I need to figure out if the line (in my understanding indicating the negative side, or the side electrons flow out of) on the diode needs to go towards or away from the power transformer.

The banded end of the diode is the cathode, which corresponds to the line end of the symbol, and the "+" marking on the original selenium.

The unbanded end is the anode, which connects to the transformer red lead. This is the arrowhead end of the schematic symbol.

The banded end of the diode is the cathode, which corresponds to the line end of the symbol, and the "+" marking on the original selenium.

The unbanded end is the anode, which connects to the transformer red lead. This is the arrowhead end of the schematic symbol.

Alright, so go by the line on the diagram, not the polarity markings. Thanks! Now the power transformer and filter capacitors are running much cooler and I can leave it on for use.