[RodB]

This is a typical power supply for radios of this era. It produces the B+ voltage for the tube plates and screen grids. It also provides a negative voltage for control grid bias in the audio circuits. Consider the casing of the 2 electrolytics to be the negative connection and don't call it ground. When the negative is connected to the chassis you have grounded it. But not in this case. The electrolytic negatives are connected to the center tap of the hv secondary creating a B- which is above ground. Thus, when resistor 47 is connected to B- and chassis ground it creates the negative bias for the audio tube grids. If you ground the electrolytics to the chassis you loose this bias voltage and the audio tubes will experience catastrophic consequences. It's very important to follow the schematic.