Ok so I always had a hum on my Robocop. So yesterday I noticed burnt connectors on my Power Board. I replaced the connectors now the Grounding issue is very bad. I get a loud ticking humming noise on the speakers. I can still hear the game music in the background. The weird issue is when coin up the game and start playing the sound will go away when I hold down the flipper button. When I let go the flipper button it gets bad again. Any ideas of where to start?

Awesome I will look more into the sound board tonight and possibly replace caps. I am also going to replace the straight pins on the power board because they were burnt.

Ok so here is what I have done any ideas would be great. I checked all the grounds and they have continuity. I replaced burnt connectors and replaced straight pins on the power supply board. More information, this all started when I replaced the connector for CN8 on the Power supply board. I cant figure out why the ticking goes away when the flippers are pressed.

UPDATE!!! I got it fixed but after another weird issue. So I replaced the Power Supply Board with a Rottendog one. I turned it on it played great then after a minute there was a puff of smoke. Well it turned out it wasnt smoke it was powder because one of the capacitors on the new board burst. The capacitor was a 2200uf 16v cap. I replaced it with a 2200uf 35v cap and now it is working fine. So my crazy ground issue is fixed and the Robocop is playing great.