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Components that have almost certainly failed will be the electrolytic capacitors. These dry out with time and the Neoteric dates from around 1970. So if in doubt it's best to replace all electrolytics.
This includes C44, the 2500µ 63v main reservoir capacitor, and C41L/R - the speaker capacitors, 100µ 25v.
C43 can also cause problems: if this has failed the amplifier may not switch on reliably. C43 is the power supply trip reset and needs to be 22µF 63v or higher,
In general, there is no problem with replacing electrolytic capacitors with ones of higher capacitance and voltage.
The mains transformer is in relatively close proximity to the inputs and, although it is separated as much as space allows, some mains hum is induced in input wiring. These two items hold coils which are rotated with the plastic piece, to minimise mains hum. In practise this works well, though the pedantic, using an oscilloscope, may notice that, because the magnetic field from the transformer is distorted, the coils can be set to minimise either 100Hz hum or 50Hz hum, but not both at the same time. So the adjustment is best done by listening closely to the loudspeakers and tuning for least audible hum.