A week ago I decided to clean my 27 year old compact disk player -A Sony cdp m79. Whereupon, I opened it up and disassembled its internal components. I cleaned the laser lens with alcohol and lens clearing paper and sprayed the printed circuit with electronic component cleaning spray. After reassembling everything the quality of the sound changed for the worse. The bass became less crisp, the middle sound is diminished and everything sound less "real" than it was before. I checked all the internal connections, of course, and everything is properly connected, there are no shorts or anything. Can anybody suggest anything that might cause this? Or know what might be wrong?
A 27 year old CD player is from near the dawn of consumer adoption of such tecnology. Maybe a 2nd or possibly 3rd generation player. Sony Gen1 stuff was audibly awful so they had nowhere to go but UP. The Philips stuff of the time, like my 1st gen FD-1000....sitting over there (pointing) were scads better but still fall short of todays even entry level player, which I suspect is where you should be aiming.
Open a museum. You have the first piecce.
As for making the player 'right'? Well, if you just want it to work right again? Re do everything you just did. Unplug and replug all connectors. Make sure they are firmly seated and clean. Some residue may still remain from the 1st cleaning. The Laser lens? NEVER use alcohol. All that's gonna do is smear around 'stuff'. Use some real photo lens cleaning solution or some dedicated lens stuff for the laser. Available Alcohol is almost always mixed with DI water.
Be careful, I think those assemblys are not only delicate, but have focusing ability.