New member with questions

Hello Group...I recently acquired a VR-5000 from a friend who used it sparingly. He did say it worked last time he used it. When I first got the radio I attached an outdoor antenna and tried to tune the 20M band on USB. I heard stations but the auto was very weak and distorted. Switching up to the FM broadcast band and changing modes to FM, it sounds very clear. I played around with trying to decipher the manual for a while including setting the clock. When I went back to 20M I found I had no audio at all. At this point I hooked up my signal generator and verified that USB, LSB, and CW seem to produce no audio. I switched the radio and signal generator to AM and it sounds fine. I am guessing something is wrong with the product detector but I also wonder if I somehow messed up a setting. Questions:

1. Is there anything I could have set wrong in the menu system? 

2. Is there a better, updated manual? Yaesu site has the same one I have.

3. Is there a service manual somewhere?

Thanks for any help...Mike W8MX