Lower volume on right side!

Question

DENON 480r amp..at least 10 years old..but over time the right channel is quieter then the left and i have to use the balance control to correct the image .seemed an intermitent fault at first but now its like it all the time!

seems like a common problem with some denon amps bulit around this time. since it seems it was a common problem..is there a common fix for it? dry joint? replace a component?

i would love a new amp but cant afford it! so out with the screwdriver and soldering iron!