Nastar repair log

Found this Nastar (on Taito B System hardware) in a lot of faulty PCBs I recently bought:

Board played fine but sound was terribly loud and corrupted :

I fired up my audio probe and started “listening” to various points of the sound circuit.Hardware uses an YM3016 DAC (SOP package, always used in conjunction with the YM2610 sound synthesis IC) 

 

As you can see from the above pinout, its pin 13 (TO BUFF) is the analog output that goes to the pre-amplification circuit (two TL074 OP-AMPs used on this board).”Listening” to this pin confirmed me that sound came out bad from the DAC :

I took a spare from a Football Champ donor board:

Installing it restored a crystal clear sound.End of job.