BTTF low speech volume??

[joeabe]

Hello everyone. I recently bought and restored a back to the future pinball. I stripped it down, cleaned it, replaced bulbs, added LEDs,etc. the machine had no sound when purchased. I bought a used sound board and the music and effects sound ok, but the voice/speech is so low, you can't hear it over the music. At first I thought the speech wasn't working. I entered the sounds test and the speech was there. I switched the 3 sound board roms with my originals and problem followed. Could it be my main board? Any help would be greatly appreciated.