/diy/ - Do It Yourself

>>2672417
>I'm assuming it's the right speaker to blame

highly unlikely.
speakers are good old boys.
they dont go bad, unless drugs are involved.
a more likely candidate is the STA540 power amplifier chip.
power amps are *born* bad.
likely, at some input level it starts to oscillate the right channel, which causes it to draw a lot of power, thus dimming the power LED.
if you disconnect the right speaker (even if you have to open it and cut one wire) the problem will likely remain, meaning the speaker itself is alright.