I acquired a Definitive Technology BP7002 speaker with a humming subwoofer. I observed a 120 Hz tone coming from the sub amp outputs when power was connected. I attempted a repair by replacing the two main power capacitors, as well as four small capacitors near the voltage regulators (see circled caps in picture). After replacing these caps, the amp buzzed loudly and the output signal was "all ****** up" (see scope picture).
Obviously, I screwed something up. But I'm not sure what kind of mistake would lead to this result. I'm about ready to abandon the repair and replace the amplifier, but I wanted to get some input from those more knowledgeable at least.
Obviously, I screwed something up. But I'm not sure what kind of mistake would lead to this result. I'm about ready to abandon the repair and replace the amplifier, but I wanted to get some input from those more knowledgeable at least.
Attachments
You need to look very closely at the SMD components where you have chipped the yellow epoxy away on the board, it's easy to knock them off completely or crack them right through where they still look in one piece but are open circuit.
Your second image looks exactly like SMPS transformer waveform.
Your second image looks exactly like SMPS transformer waveform.