I obtained an Orbitor-1 and I love it. Going through it, i found that it has a Bally AS-2518-22 solenoid driver board instead of the normal Stern SDU-100 driver board. Everything I can find online says they are the same and the game plays fine, however i have this annoying speaker hum at higher volumes that I cannot stop. I re-capped the sound board and checked all the grounds and have done nothing to the driver board... First, are these interchangeable and second, could that board be the source of the hum?
THANKS!