Pins 1 - 6 are return, pins 7-11 are power for the strings (on my T2 anyway lol)

either J120 or J121 can be used as they are identical. 8.3V seems a bit high considering it shouldn't normally be any higher than 7. Check backwards from the connectors, through fuses, triacs, etc etc and compare to known values. If that checks out looks like a wire break in the playfield



edit

Just noticed the date of last reply so if already fixed no worries lol