Twilight Zone Eddy Boards

Twilight Zone has two eddy sensors. One is at the ball eject position in the ball trough. The other is located on the underplayfield clear trough that feeds balls from the piano and gumball playfield holed to the slot machine eject.

The underplayfield sensor is rarely a problem.

The trough eddy sensor is one of the worst problems in the game, second only to the clock. It has a number of problems.

Typical symptoms are:

• Machine says "Powerball" when the powerball is not in play
• A credit dot with a "Switch 26" error.

Connector Spring Failure

The trough eddy board and its sensor are joined by a small cable. With the vibration from the trough, the brass connector pins lose spring and the connection becomes unreliable. There are two solutions. You can solder the wires directly to the boards. Or you can buy or make a new cable.

Damaged Sensor

The sensor is adjustable, and needs to be within 1/16 of the ball to work. If it is too close, the ball hits it and destroys the plastic. If it gets to the wire, the sensor will permanently fail. Although the sensor may look beaten up, the problem is still usually the cable.

Out of Tune Circuit

The design doesn't accommodate all variations of parts and conditions, and may end up being too robust and never respond to a close ball - or it may never start up. One fix to try for a stuck red light is to add some twists to the cable,

Failed Optocoupler Output

The output signal is driven by an optocoupler across the switch matrix. A short to the switch matrix can destroy the optocoupler transistor. Replace the optocoupler if the LED works correctly but there is no switch signal.

How does Twilight Zone keep track of where the powerball is?

The machine discovers the location of the powerball by using a combination of four different methods:

• 1. By using the eddy sensor in the under playfield tunnel between the piano, camera, powerfield exit and dead end that ends up in the slot. If a ball triggers the piano, camera or dead end switches and then the slot switch triggers *but* the eddy wasn't triggered in between, then we know the powerball must have gone through.

• 2. By using the eddy sensor in the ball trough

• 3. By failing to grab a ball successfully on the loop magnets.

• 4. By counting the powerball as it goes in and out of containers, such as the lock and trough. So if the machine knows there's two balls in the trough and you drained the powerball during single ball play, it'll be out the trough again in 2 balls time.