2 things happened
1. The coil diode shorted out. I am assuming it is the correct coil winding here. As it was probably working until it did not work.

Replacing, retrofitting to the pop bumper coil is 100 percent the right thing here.

Next problem.
When you turned the game on with the retrofit and a blown diode in the coil I bet you blew the transistor on the new pop bumper board. So this will also be bad. I have done the same exact thing here.

So, change the diode or entire coil and also repair or replace the pop bumper board. Ones from Rottendog will work