Yaesu FT817. Found a youtube video.
 

Hello from Dave, some time ago I had a problem with my FT817 not working on ssb. I logged into youtube and found a video dealing with this problem and the video maker showed the trouble shooting procedures and he found that there is an optional filter selection on menu 38. This was set to on when it should have been set to off. This was the same problem I had and the factory reset cured it, so I now understand more fully what can happen. You tube videos can be very informative.

Cheers all
Dave

Re: Yaesu FT817. Found a youtube video.
 

I've got an 818 (same thing basically) with the Collins CW filter. I turned this on by accident in SSB on that menu option and I thought I'd broken it because the thing sounded terrible! ;D