I was going around some pawn shops this afternoon and found a pioneer SX-3900 is good cosmetic shape. Everything appeared to work except a few back lights on the source buttons. I could only audition it from FM radio but it sounded like it should. I listened to the other sources and cranked up the volume and could tell they all had a soft static. I figured it worked for now and it looked to be in good shape. I snapped it up for 150. Brought it home, no drops or significant bumps. Plugged her in wired in a speaker and used the aux input and my phone just to make sure everything worked before I wired in everything else. The sound was SO quiet I had to put my ear up to the speaker to hear anything. Played with every knob and switch on the front and nothing affected the volume other than the volume knob and the tape monitor lever. If I put the tape monitor lever to source it gets moderately loud and extremely distorted. I've tried the phono input, aux input, AM and FM radio and They are all extremely quiet. So quiet I can hear the song louder from the actual record than I can from the speaker. I'm really unfamiliar with restoring/repairing vintage receivers/amps etc. If any one could give me some quick things to check or steer me in the right direction I'd appreciate it! I can take pics if necessary, but like I said I don't really know what to look for.