Somewhere in one of the topic threads, the question was raised whether the sound feature of so equipped BLI DC locos would continue to operate correctly after a decoder was installed. For the life of me, I can't track back and find the question and answer.
Would someone please go through the numbers on that again? Mea culpa!
With my SD40-2's I went by the book. Turns out the sound board uses CV numbers (some of which) are the same CV numbers that a motor decoder uses. For that reason they use the decoder locking scheme outlined by the NMRA. Before installing the motor decoder set CV16 to a value of 2 for the sound decoder. Then set CV 16 to a value of 1 for the motor decoder. After you install the motor decoder you can program the sound by setting CV15 to 2, back to 0 when done. Likewise you can read and write to the motor decoder by setting CV15 to 1, again set it back to 0 when done.
CV-16 locking codes:
Motor=1
Sound=2
Function =3
Lock disabled=0
When CV-15's value mathes CV-16's locking code that decoder is unlocked.
Example: When CV-15 = 1 you can read/write to the motor decoder.
If you look at the manual you will see that you have to set some sound CV's to enable sound at 4 digit addresses that were programed into the motor decoder. I had loco's that ran great with 4 digit addresses with NO sound until I realized thet fact. After making the correct CV adjustments with th sound decoder "Violla", had sound and every thing fell into place.
Jules