So, I decided to make my Haunted House a talking model...
The SC-01 emulator works perfectly, and all voices/phonemes work as they should. I installed the 64k ROM chip kit from the Davroux brothers exactly as they lay it out (a few jumper changes, a wire from one jumper point to pin 1 of a chip, two diodes in place of jumpers on another point). Easy stuff. The game boots, gives the verbal welcome, and plays like a champ (yes, I changed out the game ROM for theirs) but...
An entire sequence of sounds are distorted. They play, and one can tell they are the right sounds for the activity, but they sound like garbage. If another sound unrelated to the distorted ones plays, the game sounds sharp. Voices, all call-outs, sharp. I couldn't shake it, so I started digging into it. Eventually, I isolated the sound board so all it had was power from the game (it will boot without the MPU - all other boards disconnected) and put it in test mode. Pin 3 of U19, the S8 trigger line, is where the trouble lives. Sounds that involve S8 all sound like crap. The issue can't be coming from the MPU, or the driver board, since they are out of the circuit. All power levels are rock solid and dialed in.
I made a video of the game in play to show how it sounds:
I have emailed the Davroux brothers, of course, but I know they are busy. Has anyone either done the voice mod OR had their HH or Black Hole have a series of sounds act up on a trigger line like this?
While I'd like to just say they sent me a bad ROM, I'm not so sure. They serialize them, so a checksum won't even work for comparison with anyone else's without seeing the code.