An update, there is continuity between the J107 connector on the power driver board and all the flash lamps. When tested this had the required 20V, as does test point 7. Below is an extract from pinrepair...
LED5/TP7: +20 volts DC flashlamp circuit. Normally ON. Twilight Zone and later, this LED fades off when the coin door is opened. If off, check coin door and fuse F111 (or bridge BR4 and capacitor C11). The AC Power originates at connector J102 pins 1,2 and 3,4. It then goes through fuse F111, bridge BR4, capacitor C11, LED5/TP7 (20 volts DC), then to connector J107 pins 5,6 (and J106 and J108).
From what i figure U3 (an LS374 IC) controls the flashers, so i am assuming this may well need to be replaced.
Another intriguing factor is that the LED5 (associated with test point 7) stays on for a minute or so after powering the machine off.
Is there anything else i can test to confirm U3 is the problem or does the LED staying on suggest something else?
