Replace the foam with another suitable insulator and see if it works.
If the board works, you have sound of steam and a whistle. No bell.
I have read, but cannot recall, that there are people that repair those boards. Personally, given that sound of steam gives me a stinging headache within minutes, if the board is dead I would install a whistle or newer sound system. There are many options. You have lots of room in that tender.
I have that locomotive on our roster. Was a gift from my parents in the early 80s. It is a beautiful runner, one where MPC did not cheapen the running gear of the postwar Lionel Corporation version and it runs beautifully. I packed up the original cars and replaced them with the WBB cars which I think you will find, if you see in person, are nicer and look better running than the Lionel versions, which are cheapened versions of the postwar Madison cars. HTH.