[Yaesu] FT-757GX driver output question

[Jack/W6NF]

I have an FT-757GX with a toasted PA stage. I am entertaining thoughts 
of fitting a homebrew 6-meter transverter into the location where the 
100-watt PA board is located (I have a transverter built that will fit 
there). I would like to find out what drive level the input of the PA 
stage normally sees. Unfortunately I have no equipment with which to 
measure this output.

Thanks,

Jack, W6NF