Hello! I recently acquired a Sony WM-4 and while it plays tapes fine, there is a loud audible hum (even at zero volume). I replaced about half the capacitors while I had it apart for other repairs but it still hums. Is it a specific Capacitor I need to replace, all of them or even something entirely different? I've attached a sound file of what the humming sounds like. Thanks!
Update: the hum was coming from the wall adapter I was using since the hum goes away when using batteries but there's still a lot of just regular motor noise I need to work out.
