Hello.
I've come across a Telefunken Opus mx5550 receiver made in Germany 1964(ish). The bass adjustment knob doesn't seem to change the bass level. (it has no bass at all). Could this problem be caused by an issue with a tube or should I be looking for a mechanical problem? This unit is made where almost everything must be removed from the cabinet just to access the area behind the face. I'm not an electrician & don't want to do more harm than good by poking around.
Thanks for any help or advice,
Mark
