dac90a - to replace or leave alone??

[Bushbaby]

Thanks,
All of the waxies have been replaced with yellow aerial caps from Just Radios. As each one was replaced the set was tested and the sound did improve with each one. At the eand of this process, the set was woking well but you could definitely hear a background mains hum which is why I turned my attention to the smoothing cap (a Hunts cap from 1952 - as indicated on its side).

Steve - you may well be correct that this is breaking down under load.

Regards

Rob