Recently my FT-7 decided to not transmit on SSB. I tracked the problem down to no DC power to pin 7 of the TA7063P mic amplifier. This was due to a poor edge connector between the mother board and the audio board PB-1648.
The edge connectors are formed from wire which, over time, looses its ability to make good contact.
It turned out that track 4 of the edge connector was not in contact with the +13.8 V rail of the mother board and, as such, I was not getting any amplification of the microphone signal.
A quick fix for this was to solder a small wire between track 4 and track 9. Track 9 is the +13.8V for the receive audio amplifier. Track 4 is the +13.8V for the microphone amplifier. On the mother board these two edge connections are joined together anyway so there was no harm in joining them on the audio board.
The pictures here show the position of the audio board in the radio and the added wire on the audio board.