Is the receive audio ok? If so most of the circuits for receive audio are the same on transmit except for 1/2 of tube V5 which is a 12AX7 mic amplifier. That would isolate your problem down to a smaller area.
Did you ever run an amplified microphone on the radio? If so you might check or remove C53, a .001uf cap that limits high frequency audio in the transmit chain. Running a lot of transmit audio will sometimes exceed the voltage rating of this part and it will short out.
If you have an oscilloscope available it should be easy to trace the microphone audio from the mic jack through the mic amp then from the 6AQ5 audio amp to the final tube through R55, C37, D12, etc.
All of this is assuming the microphone is ok as mentioned before. Boa sorte!
prcguy