I've been taken to your post by a Google search, but I'd like to resurrect this thread to know whether your have made some progress or someone could be of any help regarding this issue...
Just to say that I have the exact same issue with the same amp.
Your words are correct: "a faint
buzz in the left channel you can hear with headphones or by listening closely to the speakers".
The volume control doesn't affect it, however tone controls have effect on its tonality.
The noise character is clearly is transformer buzz, like the one you can hear coming from a halogen lamp foot slider, for instance.
So, it's clearly coming from the amplifier part, since the tone controls are located on the negative feedback loop. And only on the left channel.
I've recapped all the electrolytics even the big filtering ones and the faint buzz is still there
I've tried for hours to find where the problem is coming from, testing all components, resolder everything, exchanging suspicious parts between channels, tightening the transformer bolts, pulling the transformer out of the chassis (since it's close to the left channel circuitry on the PCB)... Nothing changed.
I've abandoned since a while but interestingly, I've found some posts like yours regarding the same issue.
Here are my posts (in French
) regarding the still-not-solved issue:http://www.abcelectronique.com/forum/sh ... hp?t=64039http://www.audiovintage.fr/leforum/view ... =11&t=2075
I've put myself again in it since I have to replace the volume potentiometer.
That said, every people who came to my topics said they gave up, even helped with skills of a skilled professional technician
I've contacted even OP of old topics saying "buzz on the left channel on my L-116A". Nobody has never found the origin of the problem.
People always describe the same problem and say that it has appeared over time.
So, here is my small and humble contribution...
Hope someone could help us!