I am working on bringing a Black Knight back to life. I ended up replacing the sound board with one from Swemmer Electronics
" WSM147-4-20, Williams System 6-7 Sound w/Speech Module, D-8224 w/ROMs from Swemmer Electronics "
I have the game completely working but I am chasing an annoying speaker hum. This sound card is fed AC voltage directly from the transformer (18.7 VAC according to the BK manual). I tried every solution that I could dig up from the internet, floated the sound board, disconnected all the other components leaving only the sound card powered, new volume potentiometer, new speaker, new wires and connectors for the pot and speakers, etc. It still hums
I even pulled the sound card and powered it up on the bench with a new 18 VAC transformer to completely isolate it from the machine. Even on the bench, it hums. I tried moving all the components far away from each other to make sure that wasn't the issue and no dice.
Does anyone out there have some technical insight on this issue or experience with the Swemmer board? Is the board maybe defective? Are there any other solutions out there that anyone knows of that I can try?