ACCUPHASE E-202 restauration advises?

Hello,
I recently purchased a 30+ years old Accuphase E-202. Some of the knobs make static noise, one channel seems slightly louder, and one of the three speaker connections sounds muffled.
It appears to be completely original and sounds delightful already but I can’t help wondering what it would sound like once serviced and brought back to specs.
Would anyone be kind enough to share their personal experience and suggestions? The schematics, what to look for and some replacement parts suggestions would be greatly appreciated.
Thanks in advance,
C.