First a point about terminology so we are all on the same page. An "input" transformer is something rather different to a "power" transformer, which is what you are actually talking about.
It is highly unlikely that a 16 volt transformer would in itself cause the diodes to fail (unless possibly mis-wired in some way).
As the main rectifier consists of two diodes (rather then four) it is what is called a "bi-phase" rectifier and requires a transformer with a centre tap, like this;
However from the age and your pix it looks like this uses Germanium transistors, and as such will have a negative
supply rail, positive earth (and the diodes will be in reverse to shown above; the banded ends will go to opposite ends of the power transformer, and the unbanded ends will connect together and to the negative end of a large value electrolytic capacitor).
It is quite important to check this and get it right because if the board is powered up with the wrong polarity it is almost certain that the transistors will be damaged, and if they are germanium then it will be very hard to find replacements.
The type numbers on the transistors will help here.
It looks to me (IMG_0124 & IMG_0129) like a wire that goes to the two banded ends of the diodes where they seem to he "jumpered together" (brown?) is twisted with a blue(?) that goes to the +ve end of the largest electrolytic capacitor.
Now if these two wires went to the 16 volts bell transformer, somebody has rewired this to be a single half-wave supply. More importantly 16 volts AC will give 16 * 1.4 = 22.4 volts rather than the 12 volts implied by the electrolytic capacitor voltage ratings. This is rather overdoing it.
Originally this would have had a transformer around 9-0-9 volts, that is 18 volts centre tapped;
12 / 1.4 = 8.6
At this point it would be a good idea to get hold of a 12VDC plug pack, and being careful of the polarity, connect it to the electrolytic capacitor the diodes are connected to. This will allow you to give the amplifier a test before you get in too deep, just to try and be sure that it is still functional.
Attached are the overview, annotated; and an outline circuit for the power supply and output stage based on you pix and some guesswork.