[W8ZV]

Update to my last reply:  YUP that mod should work.  It is a cathode follower output coupling already in use.  The output from the cathode circuit suggested will do the job.  Don't have enough coffee yet this AM.  So let's ask this question about the SG-8:  Was the 400 hz tone working before you did this mod?  If it was, then you have created an issue in the AF circuit.  You might have to do some shielding make this work.  Did you replace the filter caps and any other paper caps in the generator?  That can cause issues after using the generator for a while.  They quit working and things get noisy.