FT100D not transmitting

I have an FT100D which will not transmit on any band. It doesn't even go into TX mode which means it will continue to RX when the PTT has been pressed complete with receive audio. The PTT signal gets to the appropriate input pin on the CPU, going from 4.5 V to about 1 volt. Pulling it to ground with a 1 K makes no difference. The appropriate output pin, HF/50TX or V/UHFTX doesn't change state. If anyone has any ideas, I would appreciate hearing them. The only thing I can think of is that the CPU is faulty but the receiver works fine.