Thanks for any help with this.

I've decided that my Indy 500 is going to be my first total restore and well, I'm already off to a bad start.
The first issue I decided to tackle was a burnt connector at J121 which I thought was related to some flashers and half of the backbox not lighting up.
(Side note - game was playing fine other than these lighting issues)
Turns out that the connectors at J120 and J121 were switched and also had some wires in the wrong locations.
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At this time, I decided to flip the board and check it out. There was some major surgery done at these two locations in the past as well as a couple other areas.
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I wasn't sure how far gone was too far gone in the way of repairing this so I ordered a new Rottendog through Pinball Life.
Hooked it up and got a scrambled DMD and no 5V LED. I messaged Rottendog who said to return it. Pinball Life acknowledged that they had a batch of boards with bad 5V and I must have received one.
Hooked up the replacement and things went really bad from there. All coils locked on and the shaker motor (racetrack) fired up and then the game went dead.
It blew the fuse on the power supply. Replaced that and now every time I turn it on, all coils lock on and the shaker motor fires up like before and eventually fuses F104 and F112 blow.
IMG_4111[1] (resized).JPG

I have no idea what to check next. Do I have another bad board? Is there something else wrong in my game causing this?

I'm also confused by connectors J116 -J119. The manual shows 3-wire connectors at both J116 and J117, but I only have one connector there with 3 wires.
When the game was working properly before I started all of this, it was at spot J116. (You can kind of see this in the first picture)
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At this point, I think I'm going to pull all of the other boards and see if there have been any other repairs done to them.
I could also put in the board from my RoadShow, but I don't want to mess that one up.

Any other ideas or what to check next?
Thanks

I'm going backwards but making progress....and still confused.
Pulled and reseated all connectors. While I was at it, checked the rest of the boards for repairs and I don't see any.
Decided to put the old board back in and reconnect everything the way it was, except for the repaired connectors at J120 and J121.
I put the 3-wire connector at J116.
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I can also see that J134 and J135 are switched according to the book but I don't think that matters.
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Turned the game on and, as expected, it fired right up.
IMG_4121[1] (resized).JPG

Now, what do I do with J120 and J121? The connectors are fixed but the old board is still hacked up. I'm afraid to put them on.

More importantly, does this prove that I got yet another bad Rottendog board?
How would you guys swap in this board? Would you put the connectors in their current places or would you put them in according to what the book says?
I still don't know what to make of J116 and J117 both supposedly having 3-wire connectors when there's only one present.
Thanks

Thanks for the response.
J120 and J121 are repaired. I've just been skeptical to plug them back into the old hacked up board. I'll try later today.

I'm also going to try the Rottendog board one last time tonight. If everything goes haywire like it has blowing fuses, I'll be returning that one as well as I can't figure out why it's not working.

Chris, the boards will then be on their way to you. Thanks

Thanks. That's the advice this novice is looking for.