[Arran]

Lets see, in addition to using film or a motor run cap rather then electrolytics in the power supply, the resistors often drift up in value substantially, the audio interstage transformer may be open (a common failure in any late 20s early 30s set with push-pull output) and one of the windings in the RF coils can go open, the primary I think. Sometimes the field coil will need to be repaired or rewound, I think that Mike (Morzh) had this issue with one of his model 20s, but the pole piece unbolts from the rear bracket so it's fairly easy to get the coil out for servicing. So no, a recap is only part of what needs to be done to make a model 20, or many other late 20s to mid 30s radios, perform well again.
Regards
Arran