Audio Amplifier left speaker banana plug connector cutting out or shorting

[ashtastic]

Hi Everyone,

I have a NAD C320BEE Stereo Amp, it's around 15 years old, sounds great and up until the past few weeks has been rock solid.  What is happening is the left speaker output (positive terminal I think based on the wiggle test) will intermittently cut out, or sometime slowly fade until it's out.  Sometimes, a wiggle of the left positive connector brings it up, other times it does not.  Of course I have swapped speaker cables (banana plugs) and speakers and all that logical troubleshooting, same issue.
I am fairly comfortable trying to troubleshoot along the circuit path, maybe, if someone had some idea of where to start, or what I should be looking for.  I have access to a scope and meter and all that stuff.  I do have the service manual for the amp with circuit diagrams and can share/post them if that's allowed(?)

Thanks for looking and for any help!

[GLouie]

Does this have a relay to control output to the speaker terminals? It's very common for audio amps to develop dirty relay contacts and cause this kind of problem.

[ashtastic]

yes it does, I'll check those out.. thanks!

[ashtastic]

interestingly, I've been letting it play with just the left channel, and the sound will definitely fade out and back in.  As well, when it is out, I can get it come back by just shifting or lifting the amp.  That seems to be more reliably way to bring the sound back than tapping on the speaker connections.  So my initial troubleshooting maybe be suspect.
The fading in and sounds more like a capacitor then relay doesn't it?  I could take a video and link it here.

[GLouie]

I woudn't point to anything yet without more information. I'd open the unit (probably cover and bottom panel) and operate it carefully while poking things with a non-conductive stick until it fails again. You can also try inspecting every solder joint under good magnification, and redoing any suspect soldering just for good measure.

[ashtastic]

going to tentatively say it's fixed, cleaned the relay, and re-soldered some of the joints around that part of the path (not sure if they really needed it but oh well).  Hasn't cut out or faded in a couple hours of playing.

Thanks everyone for your help!