[RGK20m3]

Another couple of common problem areas are:
Power chassis, candohm resistors frequently are off value, which can affect bias at various points throughout. Also the interstage transformers primary sometimes go open; there are work arounds besides having the transformer rewound.
Tuner chassis, open antenna and tuning coils are a possibility. Band switch carries B+, which can cause carbon tracking- there is a tread on the forum about this.