Techno Stuff
How They Work - Selection Feature Disc on Surf Club

Feature Enable

feature enable
surf club
feature trip relays
Let's get the easy part over with. Here we see that the selection feature disc trips three trip relays:
  • step 4 : [14/15] spotting
  • step 5 : add [9] to spotting list
  • step 6 : add superline

It's interesting that Bally wired the disc to trip the superline at step 6,7,8, and 9. I suppose the canny operator could clip wires on the disc to shift when the superline feature was awarded.

Note this is also different from previous games, where the trip relay would trip independent of the position of the selection feature disc.

Selection Feature Unit Step-up

disc stepup
surf club
step-up circuits
OK, let's dig in. The selection feature disc can be stepped up in single steps per coin/credit. It can also in a single coin/credit advance to enabling [14/15] or advance all the way to the superline (while enabling spotting of [9,14,15] along the way).

For any kind of step-up to happen, we need 50V on the blue wire #14-8 which is coming from mixer #2 (see the section on extra balls for a really tedious dissection of that part of the circuit). The start relay switch is in the path to prevent step-up of the selection feature unit while the spotting disc wipers are spinning.

The single step circuits are the purple and brown ones. The purple guy is used for the first two steps of the unit, and we see that the spotting disc is bypassed. This means those teaser lights are pretty much guaranteed to advance for the first three or four coins/credits unless enough good things happened to cause the 50V to be lost in/before mixer #2. The 50V on the purple circuit is passed by the selection feature disc to wire #23-2 (bottom part of the brown circuit). Why three or four coins to step up a unit twice? Because the alternator cam is in the circuit. It's function is pretty literal. For each coin/credit played, the timer cams rotate 180 degrees. Half the time the switches on the alternator cam are in one position, half the time the other.

The top part of the brown circuit is wire #61-4. This enables single stepping at steps 4 and 5 of the unit and is controlled by the spotting disc. There is a base 6/50 chance of the 50V getting through, but it is possible for the factory/operator to connect more rivets into the circuit by jumpering solder lugs together on the spotting disc. My game is set to 9/50, and 10/50 is possible with another jumper wire.

If you were taking notes, it may have occured to you that I didn't say anything about step 3 of the unit. It turns out that it is impossible to single step the unit from step 3 to step 4 (enabling the spotting of [14,15]) via the brown/purple circuits. The only way to get the unit to advance from step 3 to step 4 is to get 50V passed by the either "run to 14/15" (green) circuit or the "run to super line" (orange) circuit. Both these circuits are controlled by the spotting disc, both have jumperable odds, and on my machine they are set to 5/50 and 3/50 respectively. This adds to give an 8/50 shot of advancing from step 3 to step 4.

Note that the text associated with these circuits on the selection feature disc diagram is wrong. Wire #90 is "run to 14/15", and wire #57 is "run to superline" as shown on the schematic.

The 16 pulse cams shown in the yellow part of the circuit are what provide a pulse stream to the step-up coil so the unit advances multiple steps to reach the correct run-to level.

It appears that the trip relays in the green/orange circuits are redundant. When the unit steps up enough to trip these relays, it also steps off contacts and disconnects the 50V passing through the selection feature unit disc. In fact, they aren't redundant, and the reason is out to the left where those pink lines are coming in.

Be prepared for the following to make no sense at all.


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