Buzz problem with Linn AV5105 power amp

I have been using a Linn AV5105 power amp for almost 2 years now without issue. Up until about a few months ago, a loud buzz introduced its ugly self in the right speaker channel when the amp awakens from standby mode (it has an input sensitivity function to power down when no signal is detected). This buzz sound seems to dissipate after about 10-15 secs or so...

I didn't change any components, cables, etc. in my system before this problem occurred. I've tried the following to troubleshoot the issue:
- switched L and R speaker cables
- swapped out speaker cables for another set
- switched L and R speakers
- swapped out interconnects
- disconnected interconnects
Buzz still persists in the right channel on startup. I could live with this issue if it weren't for the fact that there is slight distortion that is very apparent when I'm playing music.

My initial guess is a dying or faulty capacitor????

Any help/guidance greatly appreciated!