ok, for now lets go with no generator troubleshooting. I'll make some assumptions here, but if the assumptions are wrong please feel free to correct
1) the amplifier itself works fine with external inputs
2) all tubes have been tested good
3) all tubes and tube sockets have been cleaned
3a) nothing has been cleaned with steel wool, bits of that stuck in the tuning fins will cause all manner of headaches
4) all tuner voltages have been confirmed in spec, schematic value +/- 15%
The last one is really important since the only part both tuners share is the power supply. They both run off the EZ80, and it looks like nothing else does so problems there will definitely kill the tuners.
If all that jives, lets start with checking the oscillator. You'll need a portable radio that you can get fairly near the reciever. Tube oscillators are pretty hot so it shouldn't need to be stuffed inside the unit, but it will need to be next to it.
On AM, set the M-F to 1000
On the portable radio, you should hear a whistle if you tune it around 1455 kc, and the whistle should move if you move the dial on the MF.
On FM, set the M-F to 90
On the portable, you should hear the white noise blank out around 100.7, and the point where it blanks out should move with the MF dial
if no joy, try reversing those numbers. Depends if its a high side oscillator or a low side. Most of them are high side, meaning the oscillator runs at a higher frequency than the station you're tuning in.
If the oscillators aren't working, none of the rest will either so may as well check that first.