OK - An update on this issue.

I replaced all the ribbon cables - no change.

I placed a Flintstones CPU board, with Flintstones ROM and Security chip - it shares the same solenoid as the JM (solenoid 2 - autoplunger). The game boots perfectly with the Flintstones setup - solenoid 2 does NOT fire. So the fault seems to follow the ROM / Security Chip.

Since I've burned a FRESH ROM, I'm looking at the security chip. Considering that the ROM resides in the Switch Matrix circuitry, I was thinking that the security chip is causing the issue as it happens ONLY at bootup - during the "Testing...." message..

So does anyone here have provisions for programming a Security Chip for this game ?