This one is kinda comical. The door tries to open for a Frenzy or loop bonus
or multiball jackpot, and then flops shut again. Repeat three times. Since the
game knows if the door is open or closed, it'll compensate by counting mirror
shots as trapdoor shots. Makes multiball jackpots much easier, but
the game is still broken. Time to fix that too.
Here are the before and after shots of the latching mechanism. Look at the two
screws with lockwashers holding a plate onto the spring-loaded solenoid actuator.
(whew!) That L-shaped plate held on by the screws has a bent-out section, which
has a shadow on it from the right-hand screw. That section is what the
trapdoor lifting crank catches on, to keep the door raised. In the left-side photo,
the crank catch (just above the crank pivot point, with the 1/2" diameter bushing)
is right on the edge of that section. Occasionally when the trapdoor lift pulled in,
the crank catch would fall off the side of the latch. By carefully bending the two
small tabs that hold the solenoid actuator plate onto the mounting frame, the
solenoid actuator plate (and the L-shaped plate screwed to it) can be shifted to
the right, getting more of the L-shaped plate under the crank catch. In these
photos, I only moved it about 1/16" over, but so far it's been enough. There might
be slotted holes in the L-shaped plate to allow an adjustment without bending, but I
didn't try unscrewing it to find out.
Here's the same mechanism from the side, better showing the crank pivot point and the
latching action. In this photo the trapdoor would be closed. The L-shaped plate
is resting on top of the lifting crank arm, waiting for the blue solenoid to
pull in and rotate the crank arm.
To open the trapdoor, the blue solenoid pulls in, which rotates the crank clockwise
around the pivot point (bottom center of the photo). When the door is up, the latch
mechanism (screwed to the yellow solenoid's actuator plate) drops toward the pivot
point, keeping the crank arm rotated, which keeps the trapdoor up. To drop the
trapdoor, the yellow solenoid is pulled in, which lifts the L-shaped plate out of
the way of the crank arm catch. Then the spring on the blue solenoid (and gravity)
closes the trapdoor.
If the L-shaped plate is misaligned, it can end up resting on the side of the
lifting crank arm, and it won't be able to latch. Here it's shown resting on the
side of the pivot point bushing. This would be bad.
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