I'm working on a Blackout with a weird issue and I'd need some suggestions please.

Game plays fine and then for no apparent reason the next time you turn it on things go wrong. The game starts up fine, press start and it starts a game, but when you hit the right flipper you start scoring points?? Also the rollovers on the lanes do not work and the knocker fires at random and then fires a few more times and then the game ends??? It doesn't act like a full reset, just ends the game and it's very random as to when the game ends.
I've recently rebuilt the power board, re-flowed solder on all connection points and replaced the interconnect between the driver and processor boards.

Any suggestions as to where I should look next?

Thanks.

bump

Yes, i did replace the sockets on the CPU.
As for the diode on the lane change switches, I checked them and they are correct.
I ran the switch test and it shows 4, 12, 20 and 28 closed. I disconnected all of those switches and reran the test and I get the same results. None of the rollover switches register at all. I also checked all of the wiring and it all looks fine, where should I look next???

Thanks

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I tested all of the diodes in the set and all checked out good, still same problem. Disconnected one switch at a time and tested in-between, same results. Completely disconnected all of the wt/ylo wires fro all of the switches and I still get the same results????

What else will cause them to test closed???

OK, somethings not right here. If I unplug the connections from the back box to the playfield I get the same readings from the switch test????

I found some and placed an order for some replacement chips for this section. In the meantime I'll try and figure out if one is bad. I swapped the 4049's and the 7406 chips individually and there was no change to the test. I'm thinking it the 6821 has a short.