Hey Everyone,
Picked up a Gottlieb Monte Carlo the other week that has been neglected for a while and thought I had it booting consistently but seems like there are still some gremlins. After getting it to boot fine (bought the new improved power supply board) walked away from it for a day and then it booted with erratic behavior (running through the coils etc). Turn it off, turn it back on, doesn't boot at all. 5 volts was going into the board, but I wasn't getting the clocking signal. Then after poking around, it started working again. Booted perfectly, 8 or 9 times without issue. I don't have sound for some reason, but that's another thread. Here's some of the things checked:
-New updated power supply board
-Grounding mods in the bottom of the cabinet (haven't done any of the ones in the backbox yet)
-Tried messing with the daughter board on the cpu, it does not affect anything (putting pressure on it to see if the connection there is an issue)
-There is zero acid damage on the board, tested the reset section and all was well (even when it wasn't booting, reset was fine)
-When testing the cpu while the board was NOT booting, it was not present on all of the pins required
-While looking through the game, one coil was melted (only one all others look good and do function when the game was running) it was the left sling shot, and one playfield fuse was blown (F11)

My main question is, can this behavior be caused by the grounding mods not being done? I am going to do them probably over the next couple ofdays, but if there is something I also need to order I would like to do so sooner than later. Thoughts?

Thanks for all that. As far as the game's condition, it hasn't been sitting in pieces, it was just neglected. It was turned on periodically so there is ZERO acid damage on the board.

Question on reflowing edge connectors, do I just add some solder to those connectors on the board?

Thanks!

So I finally did the ground mods and still having issues. I pushed on the daughter board again and it shut off. Pushed a bit and it turned back on. Seems like it’s the daughter board that is the issue. I do think the ground mods did help, but now I need to fix this. I know there is a way to fix this, but I’ve heard it sucks. There used to be a replacement piggy deux board which replaces it but it seems like they are no longer available. Are these long gone? Any sources?