[TenTec] Orion Receiver Distortion

[Bill Gaines AD8P]

I just received my "new-to-me Orion" and everything was fine until the audio from the headphones started sounding all distorted. Like it was being overdriven. The speaker audio sounds great. I have no idea what I did or when I did it. I know I am not to use mono headphones and I don't. All I have are Heil stereo types.

What did I do wrong and what can I do to fix it?

Bill