I just picked up a DH. during inspection I noticed that the knocker was unplugged in the upper left of head. Since I bought it from a location, I figured the bar didn't like the noise. On start up the coil fires exactly 10 times every time I turn on the machine. I turned it off and came back the next day and made some standard adjustments and now the gun coil fires 10 times and not the knocker. I clear all adjustments to stock and still coil fires 10 times apron start up. In the manual it doesn't say anything about that as I was figuring that 10 fires would point me in a direction of something wrong. The game plays great other than that. Any help on this would be great.

I did a coil test. All coils are operating like they should. Also I just blew fuse F104. I replaced it and worked. I made a few adjustment Like free play e.c.t. the fuse blow again. I'll do a switch test next.

Had to go back to work for a few hours. Ill check these possible issues and let ya'll know.

This might be the culprit. Not sure on the fuse blowing but replace again and so far so good.

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The game since reconnecting the opto wire has been working great until this evening. We played a few hours and at the end f the last game, I got a match and a few other things and the knocker hit a few times then stuck on and burned until the fuse blew. Not sure where to look at this point. I disconnected the knocker and the game still works great. Any help?

Well The knocker definitely has a short. The knocker doesn't have a diode connected to it. so I'll have locate it
and check it on the board.

Update sorry I had to put this on the back burner. I ordered a new coil and problem solved. I was over thinking it all.