🚀 go-pugleaf

My dad used to have a TV repair business in Palo Alto.  He once was called
to fix a set that was making a high-pitched whine.  Even back then, my dad's
high-frequency hearing wasn't too good, so he couldn't hear the noise the lady
was complaining about.  He took off the back of the set and found that there
was a Coke bottle back there.  He figured the noise was coming from the high
voltage rectifier section (this was 30 years ago, before TV's had silicon
diodes), so he shoved the Coke bottle in among the tubes there.  The lady
said that fixed the problem!

I would guess that your problem is a bit similar.  You might see if you can
shove one or more toothpicks between the secondary of the flyback and the
flyback's core.  The toroids are probably mounted horizontally with a bolt
through the center, so maybe you can tighten the bolt (or shove in more tooth
picks).  You say the toroids are in your EMI filter and surge suppressor?
Then they shouldn't be buzzing.  You'd have to have a lot of EMI to make
one of those toroids flinch.  Are you sure you aren't looking at your DC
power supply?  Lots of switching power supplies produce irritating buzzes.