Hum!!

My Jolida 102 has been great for 10-20 years.   Recently, about every hour, the thing bursts out with a loud, VERY loud base-like HUM (both channels and subwoofer).  I flip it off, then on, and it's fine.  Then about an hour or two later, same thing ...

Is this worth fixing?  Troubleshooting?  Any place in LA area you would recommend?