Need tools? Here's a video showing what I use (with links!): https://youtu.be/MLK649c1_fM
Everyone has heard that it's good to "recap" a receiver, or replace all of the electrolytic capacitors. Yeah, that's good, but not often do people talk about "re-transistoring" a receiver. No, you don't replace every transistor, but in these vintage receivers, there's always a transistor or two that's known to fail. In these mid 70s Pioneer receivers, the 2SC1451, often used as a bias transistor on power amps, is known to fail. Anytime you're working on one of these, it's a good idea to replace it with a KSC3503 transistor. And while you're at it, you might as well replace the differential pairs with KSA992 because the 2SA726's can fail as well.
EchoWars transistor testing: https://audiokarma.org/forums/index.php?threads/bipolar-junction-transistor-testing-basics.43186/
Applies to SX-434, SX-535, SX-636, SX-737, SX-838, SX-939, and SX-1010