Very nice hand me down!
There needs to be a pre-amp out, line jack to run a volume controlled and switched source over to the amp for it work normally with the receiver. Some units have them, some did not. I have a true pre-amp that I split to multiple multichannel amps for a hardwired whole house system using 14 gauge UL rated speaker wire. Hardcore audiophiles some times just pair an amp directly with a CD transport and adjust the line level. That would not be me, but some of those tube amps kits look pretty nifty.
The Luxman is a 6+1 disc cartridge type changer, correct. Do some searching, I suspect the transport was made by someone else like Pioneer. Does the single disc portion still work? If so, you've eliminated the actual laser and platter as the problem. If not, sometimes a CD cleaner with a lens brush helps and there's also the Q-Tip trick. My '98 vintage 110 disc player is a jukebox style, it front loads all of the CDs and the player transport moves side to side to pick up the disc. The belt that moved the transport broke and I replaced it myself for less than $10 from a shop that sells VCR and cassette deck parts.
Can you tell I'm still into stereo?