RS2 sound failure in Lionel Hudson "Yellow Belly" 6-18043

The RS2 in my Lionel “yellow belly” 490 Hudson (6-18043) engine quit working.   While running, the sound slowly faded , went to static then stopped. There was a wisp of smoke from the tender and the smell of burnt electronics.   The command board still operates the engine.   Tried the following to restore the sound feature.

1. Purchased new sound board, had to get one for a commodore Vanderbilt (6-18045). The description on the burnt and new board are the same; 589-699 Railsounds 2.5 rev 1.
2. Successfully tested the new board in a Commodore Vanderbilt (6-18045).
3. Placed the new board into the 490 Hudson (6-18043) using the Commodore sound chip sets and it failed to work; no sound.
4. Removed both Hudson chip set modules from the burnt board and placed them into the new Commodore board, still did not work; sound board was in the Hudson.
5. Tested the 490 Hudson sound chip sets in the Commodore Vanderbilt and they did not work. Placed the original Commodore sound chip sets back into the board and it worked when tested in the Commodore; i.e. the replacement sound board is operational.
6. Tested each connection of the 490 (6-18043) wiring harness with a VOM. All the connections were good. Moved the wires in a circle when testing to insure a good connection.
7. Contacted Lionel for the process to perform a hard reset of the LCRU board (610-8043-126). Executed their instructions without success, sound still failed.   This process was attempted using both the Commodore and Hudson sound chip sets using the sound board that worked successfully in the Commodore; both failed to produce sound.
8. Tested the speaker and POD from the Hudson on the Commodore Vanderbilt, they both worked correctly.
9. All engine functions still work correctly for the CAB 2 remote, except sound.
10. The sound board is receiving power.   When adjusting the POD some faint clicking and static can be heard coming from the speaker.

With the exception of replacing the LCRU (610-8043-126) board I am out of ideas. This board is responding to all CAB2 commands and the motor is running very smoothly. There is no sign of burning on the LCRU and no sent of burnt components. The LCRU board is very expensive and I do not want to purchase one if the original is still operational.   Any ideas would be appreciated.