I have a SX-535, it wasn't sounding right. I read up on here about it, and I replaced all the caps and transistors on the power amp board, and once I did that (and De-oxited the Pots) everything worked fine! It sounded great! Unfortunately, about 2 or 3 months later it suddenly developed a buzzing noise on both channels. Initially the volume knob had nothing to do with it, but now I get a hiss too at higher volume levels. A or B doesn't matter, and whether Balance is right or left the sound persists even in the speaker that shouldn't have any noise. Because it was everywhere at all times I suspected the power supply board, so I re-capped that, replaced the diodes, and replaced its transistors. Unfortunately, that had no effect at all, sound didn't get better or worse. I know the wiring over there looks pretty crispy, but I soldered the wires to the posts and again the sound quality didn't change so I think those connections are adequate. Poking them didn't make any noises. I'm not sure what I need to look at next. I did the power amp adjustment and got the 15mV on each side after 10 mins w/ nothing connected to the AUX input and speakers off, as specified in the manual. I also went and poked around all the transistors and caps, nothing buzzed from being touched, so I think my solder joints are okay. I can replace more stuff if I need to, I just don't know what I should look at next. Maybe I didn't do a good enough job with the De-Oxit or something?