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Tuesday 21 November 2017 at 17:16
You're good on connections. The problem is that you have a low 5 volts. Each board by itself will run fine on the bench, but with the "strain" of flippers, the voltage is dropping too low. There's a leg on the u218 chip on CPU board you can cut, if it isn't, to increase the amount the voltage can dr...
Source: http://pinside.com/pinball/forum/topic/is-this-flipper-assembly-alright#post-4084577