It works !
Thanks to Scampcamp for his pictures and Vec-tor for his clear explanations.
Finally, what was it ? I've unsoldered the green wire that linked the bulbs with the magnet. All was cabled as said by Vec-tor.
I've done several tests with others AS-2518-67 board, other bulbs, maybe during 2 hours. I've finally found :
- one of the AS-2518-67 board is out, but not the one originally in the pinball.
- one of my test bulb was burnt, something I didn't see before. And when there's a burnt bulb, no bulb is flashing at all. It may have distorted some of my first tests.
But overall, I played a complete party, what I've never done with the green wire unsoldered. And I've discovered something I didn't know (at least I didn't remember because I've played a lot this pinball during my youth) :
- the bulbs do not flash during bonus countdown
- the bulbs only flash during the start of multiball
And it's logic ! Otherwise, during bonus countdown, it's difficult to see the bonus lamps because of the flashes. And at the start of multiball, the effect is more impressive because the bulbs flash a lot less during a game.
I've put 2 orange #555 bulbs to light the Fireball, and 4 red #921 flash bulbs. It works great !