It appears your input connector has had extensive rework - which is NOT unusual for T2 and the earliest of WPC games. The connectors burnt up pretty frequently.
Do you have a multimeter? Do you know how to check continuity?
Continuity shows that 2 points are electrically connected.
I would pull the board and perform the following continuity tests first:
J115 pin 1 to ground. Note if this connection is broken, wacky GI dimming can occur.
J115 pin 2 to fuse F106 (lower left) to J120/J121 pin 11, to J119 pin 1.
J115 pin 3 to fuse F110 (lower right) to J120/J121 pin 7.
J115 pin 4 to fuse F109 (upper right) to J120/J121 pin 8.
J115 pin 5 to fuse F107 (middle left) to J120/J121 pin 10.
J115 pin 6 to fuse F108 (upper left) to J120/J121 pin 9.
J115 pin 7 to Q10 top leg (triac lower rt). Q10 middle leg to J120/J121 pin2.
J115 pin 8 to Q18 bottom leg (triac upper rt). Q18 middle leg to J120/J121 pin1.
J115 pin 9 - key
J115 pin 10 to Q16 top leg (triac lower mid). Q16 middle leg to J120/J121 pin5.
J115 pin 11 to Q14 top leg (triac upper mid). Q14 middle leg to J120/J121 pin3.
J115 pin 12 to Q12 top leg (triac left). Q12 middle leg to J120/J121 pin6, to J119 pin3.
If any of these are missing, it will be contributing to your problem. They can easily be repaired by running a careful jumper wire to connect two points on the board.
Also, run the continuity test across all 5 GI fuses. Are any blown? They can look good, but not be good!
If it all tests good, let's look at J120 and J121 next.
Are they wired properly? The T2 manual has errors, I've done several T2s, all had burnt connectors, and wired as the manual suggests, they don't work properly.
There's a color chart at Pinwiki that tells you how to wire up the J120 and J121 by using wire colors. Follow it, WMS used a standard!
If this is over your head, and you need some help, I can repair your driver board if you will ship it to me. Send me a PM.