I picked up a set of these from a wholesale liquidator auction site and had the same issue. I tried replacing the amp chip but no good. Finally as a last ditch effort before throwing them away, I cut pin 5 on the amp chip (TDA7265) which was the mute pin. I get sound from the speakers now, but they don't mute when I plug in headphones, which is fine by me. Everything else works as intended it seems. Probably not the ideal fix, but it works for me.