If all tubes are good, try larger cap values for power supply. Later ac/dc sets have slight disadvantage of no choke in power supply or field magnet /choke found in older speakers to further smooth out ac ripple in power supply. This should have some effect, especially if hum is annoying while trying to listen to set at lower volumes. Some reference books say some hum is acceptable, but by todays standards, probaly not for most people.
As a further note: A half wave rectifier will have more AC ripple voltage than Full wave rectifier output voltage using same filter caps. Give it a shot and let us know!!!!
