Philco D-597

[Reece]

Can't find a schematic either but suspect this is an AA5 radio. In 1956 it would have used miniature tubes.

Does the hum go to zero with the volume all the way down or is it still there? This would point to either a problem in the audio section or in the power supply.

Is the hum only on certain stations and not in between? That could be modulation hum. Try moving the set to a different part of the house.

Sometimes there is a heater to cathode partial short that causes hum: try a different output tube and first audio tube.