Is the added light a LED? If so, you probably have the polarity wrong. Switch the leeds and see what happens. LED's have a flat side on the bottom lip, the leed closest to that is the ground.

I'm going by deductive reasoning. It worked, you put the light mod in, it stopped working. Take a very good look at the parts that came into the equation when you did the mod. Did you move anything to get working room? Put everything back together right, so on and so fourth. Might simply be a bad ground, re-check everything. It's real easy for a minor adjustment to do strange things in a pin etc...

I would really check the polarity on that new light or even the centering of the gumball machine and motor if that came into question. Let us know, what happens because this can help people in the future who might have the same issue.

Check the wires going to gumball motor. Possible a wire broke off when you where soldering. I have a TZ. If you need any pictures let me know.

I wouldn't cut the wires. Where did you get the mod from? I have a MOD I put on mine from Pinbits.com (about 2 years ago). If it's the same MOD maybe I can help you trouble shoot the problem. Did you unplug any of the connectors around the area when you did the mod? Did you double check the wiring and make sure the wires to the motor did not become disconnected? It could just be something simple especially since you tried other boards in the game and still not working.

We mechanics like to say "If it ain't broke, don't fix it.". It's a smart policy.

I assume you've already checked this - fuses okay? The gumball motor is on the same fuse as a bunch of flashers (say, was it a flasher that the gumball light mod is hooked up to?). Check if all the flashers are working (it's the flashers around the two ramps) properly.

And, I know what you mean about TZ being hard to keep running. I've had weeks where I had to take the glass off every day...

Did you get the problem fixed?