Model 78 Skee-Ball Information

Author: Wayne Eggert
Date: 12/31/11

Introduction
This article will take a look at the early electronic Skee-Ball known as the "Model 78" with some brief description and pictures.  The "Model 78" Skee-Ball machine was made by Skee-Ball, Inc in 1978 and is one of the earlier solid-state (electronic board) based Skee-Ball machines.  In appearance and function it is very similar to modern Skee-Ball machines, however the original circuit boards in the Model 78 did not include audio circuitry and the computer is based on logic ICs (rather than a dedicated CPU IC) as many of the electronics in the 1970s were.

Pictured to the right is a 13ft "Model 78" alley.  The alley was repainted several times so the original color may have been brown with light yellow / beige side rails.  There is a winner beacon on top and you'll notice that there are no 100pt holes on this particular alley.  The older solid state electronics in Skee-Ball alleys like the Model 78 did not support 100pt holes.  The 100pt holes were introduced in the 1980s with the Model S Skee-Ball alley.

As mentioned, the gameplay itself on the older Skee-Ball machines is the same as the newer machines, aside from not having audio sound effects.  In fact, there were add-on circuit boards that could be installed in these machines to "upgrade" them and allow for audio sound effects and better ticket payout options (more on this later).  If you're looking for a Skee-Ball machine, many of these older solid state electronic machines are perfectly fine, reliable, and can be purchased rather cheaply compared to a newer Skee-Ball machine.  There's not a lot of information on them online, but I plan to help solve that =)

Circuit Board Modules in the Model 78

There are typically 3 control boxes/modules in an original Model 78 Skee-Ball.  The main control module (cpu + power supply) and then there are 2 auxillary modules (ticket/credit module and the flasher module).  The control module in the "Model 78" is often referred to as a "Model E" CPU.. the label on the control module will say "Model: E" or look something like "Model: E-X-X" (ie. E-2-3).

The ticket/credit module has a couple of switches on the front and basically just allows the operator to select from a very basic number of ticket/credit options.  These early Skee-Ball machines did not originally have any sound.  Around 1985 Deltronic Labs, Inc -- well known for their ticket dispensers in coin-op equipment -- developed the SC-700 (aka "Yogi I" ticket control board).  The Yogi I was an auxillary board for more advanced ticket control options & also contained audio circuitry as an upgrade to Skee-Ball machines (and presumably other coin-op machines) that did not have any audio.  Deltronic Labs, Inc actually manufactured the circuit boards in all Skee-Ball machines up until (and including) the Model S Skee-Ball.

Picture: Inside the head of a Model 78 Skeeball upgraded with the SC-700 ticket control board

The Control Module
The control module contains a transformer, power supply and the logic/mpu board (the "brains" of the machine).  All of this is encased in a metal box.  These really weren't meant to be serviced by arcade operators.  If the module wasn't working the operators would typically send it back to Skee-Ball, Inc. for repair or replacement.  I'd imagine most operators would have had an extra one so they could get their machine back in working order to avoid losing money while waiting for the module to be repaired.

Picture: Model 78 Skee-Ball Control Module


Opening the control module box reveals a transformer, bridge rectifier (converting A/C 12v from the transformer to D/C 12v), the power supply / driver board, and the logic board (mpu).  The wire harnesses from the Skee-Ball plug into the connectors on these boards.  I've tried to label the connectors as best I can remember, but consider the labels below for reference only as I'm not 100% certain on the ticket control / alley switch connectors.

Picture: Inside the Control Module: Power Supply / Driver Board & Logic Board (MPU)

This control module and the wire harnesses in the Skee-Ball machine (that plug into the connectors on the boards) were modified slightly for the add-on Deltronic Labs SC-700 ticket control.  Basically some of the switches and ticket control wires were tapped into and routed to the SC-700 so that for instance when you scored 50pts, a sound played (via the SC-700) as well as the score updating (via the normal logic board / cpu circuitry).

I don't have any schematics for these earlier solid-state Skee-Ball machines, so if you happen to have schematics for these please contact me!  The boards aren't *too* complicated and most of these components should be available relatively inexpensively.. tho there are likely a few components like the relays on the power supply / driver board that might be harder to track down.

Deltronic Labs SC-700 Ticket Control (Yogi I)
The SC-700 (Yogi I) board pictured below was manufactured by Deltronic Labs, Inc around 1985.  This was an add-on board that was created to add advanced ticket control and also upgrade older machines that did not have audio circuitry for sound effects.  Later, Deltronic Labs removed the audio circuitry from this board and created the "Yogi II" -- the board design appears very similar if not exactly the same, even the silkscreen annotations for the audio circuitry are there, but the audio components are not populated.  This was likely due to a decrease in demand for operators upgrading older machines and the newer Model H/S machines having audio circuitry incorporated into the MPU board.

Below is a picture of the Yogi I installed in the head of a "Model 78" Skee-Ball.  I'm not sure if the "PWM signal adjust" that is labeled is correct but the schematics mentioned the potentiometer is factory set and it appears to feed a 555 timer IC so I'm assuming it's used for PWM (Pulse Width Modulation) for the ticket dispenser motor.  I'll try to confirm this and post an update..


Picture: Yogi I (SC-700) Ticket Control Board

Conclusion
That's it for now.  I'll try to add any additional information to this page in the future.  If you have any additional information, schematics, etc on these earlier model Skee-Ball machines please contact me!