Audio Systems: speakers, electrolytic caps, powered speakers

Question
I have a pair of Acoustic Research Powered Partner speakers. They are about 20 years old. These are powered speakers that plug directly into a wall outlet. One of them sound fine, but the other has a loud hum. I have tried changing the plug wires and tried different outlets but it has not helped. Can you help? Thanks

Answer
The hum is coming from the amp inside and probably the power supply section.  Probably needs new electrolytic caps which require soldering and replacing the old ones with generic new ones.  It is not a home DIY project unless you are electronically gifted/experienced.  Otherwise leave it for a professional.