A few comments that might help.
The first red flag is between Steps 2 and 3. The power provided to the RailSounds system through the tether to the C&O tender is right off the pick-ups of the locomotive without going through any electronics. Did you try to see if the sound system would work in conventional mode? If the sound system powers-up in conventional but doesn't do anything in command, then the LCRU could possibly be the issue. (In this case, the sound system would be waiting for a command through the serial line, which it isn't getting.) If it doesn't work in conventional either, then the problem is likely localized to the sound board and its accessories (volume pot, speaker, etc.) or in the wiring from the locomotive to the tether.
The PIC and ROM chips should be switchable between the boards (although they should be kept as matched pairs). Sometimes when swapping chips I've found that they don't work on their first installation. I usually extract them again, wipe the chip contacts with contact cleaner, and reinstall to get things working. It's possible your C&O 490 chips could have been damaged by the original board, but I've rarely ever seen that happen.
Another problem is trying to reset the LCRU in your C&O. That LCRU is an LCRU1, which DOES NOT respond to any reset commands. (Your Vanderbilt has the later LCRU2, which does accept them.) You won't hurt anything by going through the steps, but nothing will happen.
If I were you, I'd go back to your working RS2.5 sound board with your Vanderbilt chips in it. Install that in your C&O tender. Test in conventional mode with your command base unplugged. If it still doesn't work, the problem is that it's not getting power through the tether, or it could be the volume pot or speaker.
Good luck-
TRW
