WIlliams No fear ground short row

maddog14

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Ok here is the problem: I get a ground short issue on the whole row 7 switch matrix. The only time it goes away is if I remove the U19 ( it has been socketed by someone else) I did not find any grounding of the wire that goes to the opto board. ( and yes , I have several LM339s that are bad on the opto board but it still displayed the ground short issue with the whole opto board removed)
I tried 3 different LM339 chips (two were brand spanking new) and also put in a brand new U20..

I cant find any shorts around the socket with my DMM.

All the tests I have done say my LM339 is fine ( the U20 tested bad and was replaced)

I must be missing something, but I cant figure out what.

anyone have any insight? Replace more chips? Could it be a problem in the U13, or even further up the line?
 
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Physically inspect all switches that relate to row 7, including the wiring that serves those switches. Ensure nothing is shorting to ground.

While I don't remember if it was row 7, the issue was very similar. Mine was also a No Fear, wound up relating to a stand-up switch on the right side that had been smashed up against the vertical up-kicker wireform. Wireform=Ground, Switch Matrix=Confused.
 
Found it. It was a short on playfield. I obviously did not ground to correct area in first test.

So now on to socketing the lm339s on the opto board and see if she will fire up and play
 
Found it. It was a short on playfield. I obviously did not ground to correct area in first test.

So now on to socketing the lm339s on the opto board and see if she will fire up and play


Awesome!!! What was shorted?
 
Awesome!!! What was shorted?

the light post lead next to the switch for the left slingshot. Of course now it wont start a game. So after I get off Work, I will repair the opto board and see what she does.

Thanks for the replies!
 
ran out of lm339 chips. waiting on a new supply.... and my u20 is blown again, damn
 
Fresh Chip for the U20 and a couple of fresh LM339 chips for the opto board, a new LM339 for the U19 previously ( along with a board repair from someone elses hack). reseated the connectors to the CPU board and she 100% works!!! WOO HOOO !!!!!!

If I magically new what to change, couple of hours worth of work. Learning to find out what needed to be changed... damn a long freaking time.

And now I have a boat load of chips LOL.... Just in case... who wants to wait longer on a stupid .89 chip.

Now I am going to thoroughly clean it, rubbers, balls, wax, polish etc and so forth.

Now if I can only figure out my Gottlieb Operation Thunder LOL
 
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