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Thursday 26 April 2018 at 11:28
Check out the diode's in the circles.
Those are the blocking diode's.
WHen one of them is broken (shorted) this can happen.
Because of the lamps and coils being in series when this happens, causes the coils to twitch and not completely activate.
Peter
http://www.inkochnito.nl
BlackBelt (resized).jp...
Source: http://pinside.com/pinball/forum/topic/black-belt-solenoid-expander-board-lights-cause-solenoid-twitch#post-4362629