There's some notoriously bad transistors in there that should be replaced on sight. They're probably your cause.
https://audiokarma.org/forums/index.php?threads/pioneer-sx-636-rushing-sound-on-left-channel.517531/
Particularly in the power amp...
awh-034 q1 2sa726 x x x x 512-KSA992FBU...
I saw an ad for "JBL speakers" for $300 that were located about 3km from home. They looked like 4311s in the picture so I contacted him and said I can pick them up at his convenience. He responded that I could pick them up in about an hour. We were having an ice storm that day so after scraping...