wrong sound and solenoids is likely a momentary solenoid data problem. I'd suspect MPU J4 if both sound and solenoids have problems. Also driver J4 and sound J1. In the schematics check the signals labeled SOL-A to SOL-D (and SOL-E for the sound board comes from MPU J1 P7).

Sound board uses most of the same signals as the solenoid driver board so very likely mpu j4 connector could be causing both issues.

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if the sol/snd bank select is open circuit at MPU J4 yes.

red wire out of the connector is going to make the wrong solenoids fire. check for similar problems at the sound board and MPU J4

Make sure the isolated 43v return is connected to ground. May have to look at the wiring diagram. I can't remember if it goes to rectifier or sdb.