This should help you :
Please check out page C-54 in the manual ( you can download it at jerseyjackpinball.com ) that page shows the data harness path. From W6 to #29, to #1, to #2, to #3, etc. etc.
Please go into Tests - LEDs - All LEDs, this turns any working all white. Lift playfield and lean on backbox. You can see the working ones kind of glow.
They are wired in series, a straight line. Find the last working one, the one after it that is out is the bad one. With the power on, you can by pass the data harnesses on the LED boards, bypass the bad one, and turn off in settings. ( be sure and turn it back on when you replace it ) this will help you identify a bad one.
As an example, say #15 was out. You can run the data harness from red on W2, to green on #16 instead of #15. If the rest light up, you know #15 is the bad one.
With the power on you can move data harnesses. They go red to green from board to board. Don't mess with the power connectors with the power on.
LTG : )