Oh, that others would go through such trouble before posting.

To confirm your worst fears, it yes, it does appear to be something internal to the receiver.

Now, the good news: Since everything else seems to work jake, it seems to be totally isolated to the test tones.

What to do?

Well, if you're a gambling man you could kerfutz around in there but I can't really tell you what to look for or what to do. All switching seems to be done electronically so looking for something physical might not work out too well.

Or, you could send it out and see what it would cost to repair. Have smelling salts ready when they give you an estimate.

But, if you're like me (a cheap klutz), I would be tempted to leave it alone and be thankful that everything else works. I believe you can pick up test DVD's that have test tones on them.

good luck...