Can you identify both switches on the switch matrix diagram? If they are in the same column or row, check all switches in that column or row, including other not affected switches, for broken or missing wires.

215B2ACB-9148-4AB1-90D3-90BDA7E35EE0 (resized).jpeg

Nokoro is on the right track here, I'm guessing it's a broken wire or diode at any of the 6 switches of row 8. Here's the row of switches shown on the schematic: 2045805753(1).png

Note the wire color for that switch row is white-gray. This means you want to find each switch on row 8, and make sure that the white wire with gray stripe is firmly attached to the solder lug on each of them. There will be multiple white/gray wires at certain switches because the circuit "daisy-chains" from one switch to another switch on its shared row. I made a little red mark next to each switch in the row: 16,24,32,40,48,56 1818734574(1).png

Gently tug the white/gray wires at each of the 6 switches marked above to be sure they're firmly connected. You may find one broken off already...if you do, you found to problem--solder the wire back onto the correct switch lug. Next check the diode on each switch. Make sure the diode isn't touching anything it shouldn't be, and that it's also firmly connected at both solder lugs on the switch.

If all the wiring and diodes are properly connected, next I'd verify you can get continuity from every white/gray switch wire up to the connector at the mpu J3, pin 1 (which is that same white/gray wire, just where it leads up to the mpu). If continuity is good up to there, you may have a bad solder joint or header pin at J3 on the mpu or another problem with the mpu.

Make sure you report back on what you find. And remember, it could be any switch in that row, not necessarily #7 rollover.

Good luck! You’re close!

No prob! Did you find the other switches i marked on the list are working? I've often found if a diode or wire broke off a switch, it can often cause *all* the switches on the same row or column to stop working as well. That's the reason I'd recommend checking the wiring and diode at all 6 switches i marked--a break at *any* of them can sometimes cause all of them to stop registering. See what you find, and let us know how it goes!

Also, be sure to stop in and ask any questions you may run into along the way. It took me a *long* time before i could read schematics and stuff, so i can understand how daunting some of this stuff can be. Ultimately, a lot of problems on these games are due to bad connectors and broken wiring (generally due to years of vibration)... and where there's a will, there's a way! If you're determined enough, you *will* solve the problem eventually!

Good luck!

I will reiterate this point. 6 years ago, I knew absolutely nothing about electricity or how these machines worked. It takes time, but with each repair, you learn a little more, gain confidence and knowledge, and become better prepared for the next one. At some point, you will cross over from being bewildered to actually intuiting what is wrong. That said, there’s still so much I don’t know and have to learn . . . .

Great stuff, man!

Enjoy!