I just noticed a mild, but audible hum in the lfet channel. I did all the tests to narrow it down to the crossover itself, not cables or other hardware in the monitoring chain. It unit is obviosuly quite old as an original piece, as I bought it used in 1995, and it was already faitly vintage at that point.
I wonder if it is aged caps that creates the problem, and if yes, how hard is it to change the caps? is this something I can do myself? I can solder fairly well, but I know little about the theory of electronics. What parts are the most likely to be culprits and what should I replace them with?

Thanks