Rotel RA611-Left speaker channel produces sound but only just ?

I still have a Rotel RA611 that I bought new. Only used occasionally in my home office it has recently decided to malfunction on the left channel only. Sound is there but even on full L/R balance separation it can only just be heard. It makes no difference if the speakers are attached as speaker 1 or 2 or both. Fuses are fine. Any ideas please on where/how to look for a solution or indeed is there a solution? Any help will be much appreciated as I am loathe to get rid of the old girl as I have had her longer than my wife and family!