Multiplex Microphonics HH Scott 350 A

Hi Folks,
I have an HH Scott 350 A tuner that I've been investing in little by little. It wasn't all too long ago that I replaced the tubes in the multiplex section with military grade Telefunkens. However, playing in stereo resulted in a garbled gravel like sound and being as such, I only played it in mono. Then my capacitors went south, so I recently had it worked on by my tech and he got it up and running and did a good job of aligning the multiplex by ear. Even the separation is to my liking. The problem now however is that when played in stereo mode, I'm getting microphonics. It sounds like someone is down the hall and improvising on a silver triangle whenever the music begins. I do know about Herbies tube dampeners and I plan to give that a try. Eventually Mapleshade seems like a solid option for when I have that type of cash flow. Does anyone have another other suggestions? As always, much appreciated, thanks!
Maybe I should rephrase my question; does anyone have an idea as to where the high pitched ringing sound is coming from when I turn on the Scott 350 A stereo selector? Does anyone have an idea as to what needs to be done in order to fix it?
Thanks Again!