JBL 4312 Speaker issue

[jpk]

I have recently just got my old stereo system back up and running. It has been quiet for about 20 years. It has a Sony receiver and a pair of JBL 4312 control monitors. Upon turning on the system, the output of the right channel is substantially lower than the right. What might the issue be?

 

[Vladimir]

Dirty pots and switches most likely. The receiver needs to be opened and cleaned with electronics cleaner,