Cleaned my share of contacts over the years.
Like everyone that sat for years.

The horn gounds to the core support.
On my last bird, only one worked.
Turned out the other was rusty where it bolted to the support, which was also rusty.
Cleaned and painted them, then moved the horn back and forth just enough to get a bare spot. Works like new.

Bty, i dont like the tone on mine.
What do do guys use? A & F, or what?