Okay so Sunday night my Congo is playing, but I notice that instead of locking balls in volcano it is registering them, but then kicking it out instantly. I still get my lock but instead of a ball coming to shooter lane it comes back out of Volcano. I went to go into test mode and the my test buttons / direct switches weren't working, coin switches still worked. Planned to come back Monday with all my tools and fix it. I get there Monday night and game is still taking credits, but start button no longer works. Repin my direct switches connector at coin door interface board and this fixes my test buttons so I go into test mode. No switches in column 2 work at all. If I press any other switch on the playfield I get a row ground short error for the corresponding row (seems to happen to all 8 rows). Planned to swap out U20 tonight. Does this seem like the right path to be taking or am I likely looking at 10 opto board issue under the playfield?

pasted_image (resized).png

I did also disconnect the switch row and column connectors from CPU and use a jumper wire to test the pins on the cpu and the short continued to come up.

Okay U20 seems to have fixed most things. Replaced it last night and was able to play game. Once lock was lit and I shot into the Volcano my optos in there weren't recognizing the balls. I looked at schematic and they all run back to 10 opto board, and the U3 chip on it. Only other issue I found was that when I spelled GRAY and went to lower playfield the left flipper wasn't registering, both lower and upper left flippers worked fine during gameplay but not on lower playfield. I have a feeling they aren't related but just wasn't sure. Any help and advice is appreciated.

Alright all issues fixed.

Swapped 10-opto board from my Shadow into Congo and everything was working again. Discovered a broken wire on the coil for the left flipper on lower playfield gorilla mech, realized this is what must have broken and then caused things to short out blowing both U20 on CPU, and U3 on the 10-opto board.

Decided to leave 10 opto board from Shadow in Congo so it would be working again on location, and to try my hand at my first board work de-soldering the U3 chip from the original broken Congo board.....bad idea....lifted a trace while removing the chip. Should have left it to a pro, will try to run a jumper wire, but the fact that the board was readily available I figured it was worth trying, and realistically with a jumper wire it will probably still work. Anyway if anyone else has something similar happen hopefully this can help them in the future.

Also I don't know what is factory correct at this point as obviously my Congo has had a long life on route, but the wires going to my coil on the lower playfield were in a harness support that caused them a lot of tension, I moved and adjusted it to a different support under the playfield to keep it neat but allow it a lot more play, also heat shrink was applied over the coil connections so if it does break again ideally it wont be able to short other things out.