As I wrote earlier and long ago, the beauty of good 70s audio gear is that just about everything is done using discrete components only - which makes these beasts eminently repairable (if you have the service manual as I obviously do).
My Sanyo had developed a very bad left channel (not just crackling but bangs that threatened my speakers) and I figured it was a problem with the main amplifier, likely close to the power transistors.
The relevant NEC 2SB541/2SD388 transistors have of course become unobtainium long ago, but reading up on these in various transistor substitution documents I found that Motorola MJ21195/21196 are workable replacements (with somewhat better ratings). It cost me just $11 for two transistor pairs, $4 for new insulating/heat-conducting rubber pads and about half an hour including the offset/bias adjustment to revive the DCX. As far as I can tell the problem was the rotting, super-thin insulating material between the transistors and the heatsink, but I replaced the transistors nevertheless.
Good as gold again, and it may yet outlast me.