Have you tried simulating the test switch closure with a jumper lead across switch strobe and switch return at the MPU board edge connector?

I don't mean to be insulting here (honestly!), but, did you repin the connectors for the switch matrix? If so, is there ANY chance the pins are on the wrong side of the board (Didn't use original housings)?

IF you know its not the above, then do the same jumper trick at the very first occurrence of the same two wire colors at the playfield. Preferably, before any diode strips.

Like I said, BEFORE the diode strip(s). You want to simulate exactly what you did at the connector (which you stated worked). So do the same thing down on the lower cabinet (for coin door) or playfield (for playfield switches). Then, you want to do the same for the other end of the switch. Or, at least the first occurrence of the wiring in the lower cabinet. Attached is a snipet of Black Hole's lower cab. switches.

We would need a photo of the switch matrix drawing(s) to give you more detail as I don't have a Genesis manual to look at.

bhcabsw (resized).JPG

I know the playfield switch harness probably plugs directly to the MPU board, but does the lower cabinet switch wiring go directly to the MPU edge connector or is there a molex connector in between to allow you to disconnect the head?

Continuity (Beep Test) is rarely a good thing when working on pinballs. If you are using the Beep as your indicator, some DMM will trigger the beep for anything lower than 200 or 300 ohms. Unless you are actually looking at the ohm value and comparing that value to what you get when your leads are touched together (like 1.2 ohms etc.) than you should not trust what your ears are hearing.

Try adding your own diode in line with your jumper. You can try a 1N4148 or 4004 etc. The problem is, they have a higher voltage drop across them (than the original ones gottlieb used) which may be exactly what your issue is (too much loss before getting back to the ICs.)

What do you read in diode test across some of the diodes with you DMM? Did you try using an external diode?

Unless HV was put across the diodes, I find it hard to believe all the diodes are zapped.

What ICs is Schwermer using for 7404 and 7400 in Switch matrix?

Is it a multiball game? If so, the start process won't continue until it sees a ball sitting on the max ball switch on the ball trough ramp. And, if a 4 ball game, a ball also on the outhole switch. Gottliebs will seem to go completely dead until they can account for all needed balls.