Lionel Trainsounds - main pcb repair ?

I had a trainsounds diesel that went crackly, then hummed, then went silent.  After much troubleshooting, including replacing the trainsounds board with a known working board, it turned out to be the speaker.  If you have a known good speaker, I'd give that a try.

If it's the board and you're getting loud hum, the first part I'd replace is the filter caps.  I suspect the biggest cap would be my first target.

I think I was able to find the issue in one of my boards. It's most likely dead sound chip!
I was able to swap sound chips between 2 boards and 1 of the boards started to work!

The chip has symbol MC908Q4CP ( which is DIP8 package truncated name for MC68HC908QT4CP) and it comes from PCB which was originally in Lionel 6-28857 Alaska GP-7 Diesel Locomotive #1804. Here are my questions:

1. Can I buy somewhere chip with sounds to my Lionel locomotive ?

2. I can have access to (e)eprom programmer. Did anybody try to successfully clone Lionel sound chip ?
3. Can I assume that all Diesel Lionel sounds are the same and try to clone sound chip from any other Lionel Diesel Locomotive?

I appreciate your help.
Chirss

Seems like a lot of effort.  But, the PIC has the program, so if it is bad, you get the whole board from Lionel.  Not sure I have seen anyone discuss what you are asking, especially for a conventional train sounds board.  G