I suspect that where you mention V4 6EJ7, really is meant V3, 6CB6 the pre-mixer. Interesting that the solid state balanced modulator was the source of the problem. I have the same type. The 2SA695D pnp transistor acts as a current source. The "D" specifies an hfe range of 90-180. The current is controlled by the carrier potentiometer at the back. It sends a current to forward bias diodes D2 and D4 to unbalance the modulator. Fet Q1 is a source follower delivering the 8998.5 and 9001.5 kHz crystal frequencies to the diode modulator, fet Q2 is the output amplifier which goes to the crystal filter. VR1 and TC120 are adjusted to balance out the carrier. Pin 9 is where the audio comes in from the microphone amplifier.