Receiver Balance Issue

I was given a  Harman Kardon HK 3470 with a pair of Klipsch KSB 3.1 speaks over the weekend. To start, I am not an expert on audio equipment by any stretch. Well, I installed a few car stereo systems when I was younger and know about some of the bigger players and better brands. Beyond that, I just enjoy listening to music and like it sound as rich as possible. So, please forgive my ignorance. From what I was told the equipment has sat unused in a dry basement for the last 10-12 years. When I connected the speakers I noticed the right channel is significantly quieter than the left. In troubleshooting the issue, I have done the following.
-  Turned the Balance knob all the way to the left and all the way to the right. When I turn the knob about 98% - 99% to the right, the speakers sound almost balanced. When the Balance knob is turned 100% to the right and I turn the volume up to about 25%, the right speaker gets louder as expected however, I can also faintly hear sound coming out of the left speaker.
- Switched speakers between right and left terminal connections. The issue stays with which ever speaker is connected to the right terminal. The receiver has terminal connections for two sets of left/right speakers. I switched the speakers between the "Speaker 1" and "Speaker 2" terminal connections. The issue stays with which ever speaker is connected to the right terminal
- Changed source input (i.e. radio, CD, Phono, Aux, etc.) Issue persists no matter the audio source

Short of opening the case and looking for any bulging/discolored capacitors or blown fuses I really don't know what I can do. Therefore, any suggestions would be greatly appreciated.