ALC pegs on SSB but no output, too high power output on others


 

My "fixed" IC7000 has a transmit problem. 
It seems to be OK on receive but on SSB the ALC pegs with even the least audio and it puts out no RF power.
On RTTY, CW, etc it seems to put out too mucheap power.
Any thoughts as to where to start looking?
I have replaced the ribbon cables from the main board to the PA board as the old ones cracked while working on the "Click Click" problem.