Picked up a fairly cheap sp that had lots of corrosion on metal parts (power switch, charge port, and volume slider). After cleaning it all up and replacing the volume slider and audio cap, it still had low volume.Turns out there was a broken trace between the volume pad and the U6 (There should be continuity from the via I solder to, over to the via right next to the s in SW11). Adding the bodge fix the issue.