Nakamichi AV-500

I just found at the local pawn shop a Nakamichi AV-500 receiver on the "as is" table for $10.00. The manager said that it had no audio output. It had the normal wear & tear on the display & a few scratches on top from being stacked on. I then noticed the A/B speaker switch was on B. I paid my $10 & went straight home. I switched the A/B & just hooked my up BAMTM's with my Oppo for a quick 2 channel test. Diana Krall never sounded better. I can't seem to find much info or specs on this receiver. I do know it weighs over 30 pounds, so the power supply must be massive. If anyone could shed some light on my find, I would appreciate it.