Next on the repair agenda. My Brother's Sony STR-K840P Receiver. It goes into intermittent speaker protect mode. I suspect a cold solder joint on either the output devices or the regulators. Very common issue with these late 1990's /early 2000's receivers. I tired flexing the main board with power on but so far still working.
Sony and the other audio manufacturers have gone cheap on their designs. Used to be there was a bottom plate you could remove to gain access to the backsides of the boards and check the solder connections. No more. That board and all the interconnects has to come out in order to access the backside. I've heard that many repair shops will refuse to work on them because of that. I don't blame them. But I'm gonna give it the old college try.
Yes, this construction is truly disgusting. Especially as the connectors are the typical consumer quality and the PCB is sometimes not easy to extract even with the wires gone.
When I work on such stuff for friends and it doesn't have a very solid commercial reason like a collectors item yielding 4 digits, I tend to cheat. Last one was a amplifier of similar construction. two mosfets gone - after localizing them, I cut a square out of the bottom and fitted a little lid over it after performing the repair. Another brought in a amplifier of a bit higher class (H-K, if I recall it right, but I am not very attached to this stuff) where the protection circuit was continually off. I found that of all the components involved, a little 220/12V transformer, which was part of the protection circuit's supply, had a secondary open. I located the primary and secondary tracks, cut them open and scabbed a better transformer on a prefabricated PCB onto the side with a adequately secured wire harness. repair time 30 min after diagnosis.