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A.C.M.E. Electro-Mechanical Slot Machine
Troubleshooting & Repair Guide

(CLICK ON ANY PICTURE TO BRING UP A LARGER VERSION)
Introduction
An electro-mechanical slot machine is more mechanical than it is electrical. The electric components are mostly motors, relays or solenoids, it's the mechanical parts of these assemblages that really need the maintenance. The electric components can further be simplified as being wire wound around some iron... electro-magnets. These electro-magnets make motors spin, relays switch and solenoids contract when power is applied. This type of electric device is very robust and rarely if ever burns out. The other electrical parts are light bulbs, fuses and wire... not very complicated and are all some form of wire as well. You will not find "electronic" components in these machines like resistors, capacitors, diodes, transistors etc. everything with the exception of the coin acceptor is electrical, not electronic.

These A.C.M.E. slot machines run on 115VAC (volts alternating current) at 60Hz (Hertz or cycles per second) which is standard U.S. power. These machines can run on 50Hz at 110 volts AC with a simple wire modification on the power transformer. The motors will run a little slower than with 60Hz power but this will not effect the overall operation of the slot machine.

*** NOTE ***
Do not alter any wiring inside of the slot machine. If you notice that a wire is broken from its connection point and it is clearly evident where it was connected, you can solder it back in place without much concern for short circuits. It is highly advised to become familiar with the schematic for the area of concern and trace the circuit before attempting any repairs of this nature. Use a digital camera and document clearly the condition of the problem area so if further assistance with the problem is sought, the repair technician can plainly see how it looked before you messed things up. :-)

*** NOTE ***
It should be noted that these machines precede the digital age by a bit and thus make no concessions to electrostatic discharge and radio frequency interference. They can cause clicks and pops in radios, televisions, computers and the like near the operating slot machine. These are harmless but can be a bit annoying. To guard against this type of thing, put the slot machine on a power circuit which does not have these other devices connected.

Major Assemblies and Components
There are 3 removable component assemblies in each slot machine with the rest being mounted to the component tray in the lower cabinet section. In addition, there are lamps, both incandescent and fluorescent beneath the marquee and reel cover as well as above the coin tray. Finally, there is a bell and a horn mounted behind the marquee.

Removable

Reel Assembly (upper cabinet)
The reel assembly contains the following major parts or assemblies: play reels (1), cam (2), cam follower (3), pay boards (4), motor (5), control switch(s) (6), and connector (7). This assembly can be run outside of the slot machine by applying 115VAC power to the 32:1 gearbox/motor with cam switch 2A interrupting the motor power.

Service - Reels Service - Cam Switch

Maintenance for this assembly is basic dusting or wiping with a damp rag moistened with denatured alcohol. Do not use the damp rag on the reel faces (where the symbols are). This is paper and will stain if it gets wet. Never use oil or grease on the mechanical linkages, all pivots and joints are designed to work properly without lubrication. If operation is stiff or sluggish, disassembly and cleaning of the mechanism is recommended only. A light spray of contact cleaner/lubricant on the contacts of the pay boards and wipers can reduce noise and improve payout accuracy but once again, not heavily or often because this material builds up and can become tacky and sticky. If this occurs, clean the pay boards and wipers with denatured alcohol and be careful not to splash the reel assembly in the process.

Service - Stop Pawl The most common failure of this unit is "free-wheeling" where once initiated, the reels will repeatedly spin. This is usually caused by one of three things in the following order: 1. the motor brake is sticking which causes the motor to spin past the stop switch (cam switch 2A). 2. Cam switch 2A is not closing properly or 3. the cam disk is loose on the cam shaft. If the motor brake is suspect, remove the motor and disassemble the brake mechanism which consists of the actuator, stop pawl and the stop pawl spring and the post and washers that the pawl is mounted on. Clean all the parts with denatured alcohol, re-assemble and check for free operation. A sticky motor brake is sometimes characterized with a buzzing sound when the brake should be applied.

If the cam switch is suspect, carefully observe cam switch 2A/2B and make sure it is opening when the screw in the cam disk hits it, if not bend the leafs of the switch so the contacts open and close with actuation. Burnishing the contacts with 600 grit sandpaper may also help.

Service - Cam Align If cam disk #1 is loose on the cam shaft, tighten the allen screw in the cam disk's hub. Use this diagram to approximate the correct position. Although exact alignment is favored, having the disk not spin in relation to the shaft is more important. Cams #2 and #3 are affixed to a toothed pulley wheel and are positioned on the cam shaft by way of a flat ground on the shaft. Cam #1 does not have this flat and can be fastened at any rotational angle. Make sure to match the angles (by eye is fine) in this diagram or improper operation will result.

The second most common failure is a "dead wheel" where the reels will spin but nothing happens after that and the reels eventually stop at random alignments. Three areas can be the cause of this, a bad variator, bad interconnection or cam switch #1. You can refer to the section on the Variator if you suspect it. You can wiggle the connector and make sure it's fully engaged if you suspect the connector, otherwise take a look at the reel assembly cam switch #1. Observe it's operation and make sure it is closing and opening on queue. The loose cam disk #1 problem can cause this switch to make contact at the wrong time. Check the cam alignments.

The last area of possible trouble is in the pay boards and wipers. These are actually large, multi-throw rotary switches. They have a very large 34" diameter pattern so they only have a few degrees worth of the total rotation on the boards. They have 25 positions and 15 rows of which 8 rows have contacts for a total of 120 contact points per board. Only a small amount of these contact points are actually used, one position each for every symbol type on the reel and 2 to 5 rows of contacts for each position.

Service - Pay Boards The wipers are pulled in contact with screws installed in the star wheels of the reels which position the wiper contacts with the appropriate contacts on the pay boards for the symbol displayed on a reel.(that's a mouthful!)

Because they are not enclosed, over time, the pay board wiper assembly will get dust mixed in with the contact lubrication and thicken, making the wipers stick or move sluggishly. This causes all kinds of payout problems. If you suspect or witness this happening, don't tighten the springs that pull the wipers to the star wheels, this will just wreck them. You will need to clean the pay boards and wipers with denatured alcohol and then re-clean and lubricate them with a spray T.V. tuner cleaner/lubricant. Be very careful of the wiper contacts, although they look very strong, they can break easily.

Care should be observed when handling the reel assembly because the wipers can move freely and wind up in the strangest places. If the reel assembly is placed on its back, the wiper arms can fall out from between the pay boards and get stuck on the board edges. The wipers can wind up on the other side of the star wheel screws where they freeze the reels. Make sure the wiper arms are seated correctly before using the reel assembly, and most important, never operate the reel assembly in any position other than sitting level and upright (oriented the same as in the slot machine cabinet).

Payout Hopper Unit (lower cabinet)
This unit receives all the deposited coins and pays them out when a winning combination is matched. The circuit for this unit is very simple with two wires to power the motor and two wires for the coin switch. This unit can be run outside of the slot machine by applying 115VAC power to the motor.
Service - Coin Hopper
Coins drop into the hopper (1) where they are stored until a payout happens. If there are more coins than the hopper can hold (around 300) the coins will spill off the end of the hopper and fall into the coin box lower in the cabinet. When a payout happens the motor (4) starts and the coin platter (3) begins to turn counter-clockwise. Pins in the platter scoop coins out of the hopper and convey them around to the top where the blade (2) routes them off to the coin dispenser chute. While the coin is on the blade it lifts the counter lever (6) which actuates the coin switch (5).

Service - Hopper Switch Maintenance for this assembly is basic dusting or wiping with a damp rag moistened with denatured alcohol. The only real problem this unit could have is if it does not count out the correct amount of coins. There are two possible sources of this problem. First, the coin switch could be improperly adjusted or, the motor brake is sticking. If you suspect the motor brake, refer to the "Reel Assembly" section on the procedure for that type of failure.

If you think the switch is the problem, place a coin on the blade just where the counter lever is, pushing it to its uppermost position. Re-adjust the coin switch by backing off the locknut and unscrewing the adjustment screw to assure the switch lever is not depressed. Screw the adjusting screw in and listen for a "click" from the microswitch. Once you get a click, advance the adjusting screw another full turn. Tighten the locknut making sure not to rotate the adjusting screw.

Some coin levers have an assist spring to keep the "bounce" at a minimum. Usually this is not required but the tolerances of these manufactured parts sometimes necessitate this small boost.

Coin Acceptor (upper cabinet)
The Coin Acceptor is the only electronic device in the slot machine. It requires 48/50VAC as well as 6VAC. Running the Coin Acceptor outside of the slot machine will require a power transformer with 48/50VAC and 6VAC secondaries.

Service - Coin Mech Service - Coin Schematic

Referencing its patent number: 4,334,604 shows a date of July 14, 1982, however, the mechanism show a patent applied for number of 021305 and was in operation as early as 1974 which kind of shows you just how long it takes to get a patent. This coin acceptor operates upon the principal that the inductance of coins vary from one type to another and the application of a coil attached to a tank circuit can detect the difference in the inductive mass (gauss) of a coin and determine whether it's valid or not. There are two potentiometer adjustments on the circuit board that determine the low and the high trip points for the tank circuit.

Service - Coin Adjust Adjusting these is very touchy and requires not only the supply voltages be applied, it also requires the magnetic environment (grounded metal bracket) that it will operate within. In the shop I use a test fixture to accomplish this which provides a near identical environment for adjusting coin mechanisms of this type.

The procedure is to dip a coin in the top of the coin acceptor where the sensing coil is and see if the acceptor relay clicks in. When the coin is removed from the slot the relay should click out. Using a completely plastic screwdriver so as not to influence the inductive field, rotate the center potentiometer (upper limit) and the one to the left side (lower limit) until the coin mechanism behaves as I have just outlined. Sometimes the acceptor relay will jitter, this is a sign that the balance between the adjustments is too fine or close, re-centering and adjusting again will zero in on the proper adjustments. This is a tedious and fiddly process and can take a lot of time out of your day. If at all possible, avoid adjusting this device, getting a proper setting with these potentiometers is about as hard as hitting the jackpot on the slot machine.

Mounted

Power Transformer / Fuses
The power input for this slot machine first goes through a multitap power transformer that accepts either 115 or 110 VAC and provides 48/50VAC and 6VAC on its secondary. The primary is fused with a 5 amp standard 3AG fuse shown in this diagram as 115VAC. All fuses are 3AG size.

Service - Fuses The fuses shown here are the main power distribution for the slot machine. Take note that both the reel motor and the payout motor have their own separate fuses and these are the slo-blo type (SB). The wire colors are matched for the circuit throughout the machine where blue is 6VAC, orange is 48/50VAC, black is 115VAC, red is motor control power and yellow is the common AC return for both 6VAC and 48/50VAC circuits while white is the 115VAC return.

The fuse block is the first stop when troubleshooting the slot machine. Make sure that no fuses are blown before checking any other circuits or systems in the slot machine.

Rotary Stepper Switch
The memory units for the slot machine are these rotary stepper switches. Two types are employed in the A.C.M.E. slot machines, one called the odds unit which counts and remembers how many coins have been deposited and the other type is called a payout unit, which counts and remembers payout amounts. The capacity of the payout unit can be expanded by multipliers (see the section on multipliers). All solenoids operate on 48/50VAC.

Odds Unit Service - Odds Disk
The odds unit consists of a contact disk (6) with a wiper (7) which is rotated from contact to contact by the toothed wheel (8) which is advanced by the step-up solenoid (1) and reset by the reset solenoid (2).

Each solenoid has an "end of stroke" switch, the step-up E.O.S. (4) and the reset E.O.S. (3). a third switch group (5) is present and referred to in original schematic diagrams as a 2nd STEP switch but I think it's more appropriate to call it an "end of rotation" or an E.O.R. switch.

Although the odds unit has 50 positions, it is physically limited to 3 positions, one for each coin played by having one tooth strategically shaved off on the toothed wheel (at the 11 o-clock position in the picture above). As coins are dropped into the coin mechanism, the wiper advances counter-clockwise as viewed from the contact disk side once for each coin deposited.

Maintenance for this unit is basic dusting or wiping with a damp rag moistened with denatured alcohol. Many problems in payout, coin handling plus lighting and display can often be traced to this unit. Bad contact continuity being the most prevalent. Removing the wiper and bending the contact fingers down a bit can increase the contact pressure. A good cleaning with T.V. tuner cleaner/lubricant works wonders and even possibly some contact burnishing can alleviate contact problems. Don't forget about the switches, they get dirty too and a good wipe and burnish can bring them back to life as well.

One last potential problem is the unit not resetting fully. This is caused by too much friction in the rotating assembly. The way to fix this is to disassemble the unit enough to remove the toothed wheel. Once removed, a good denatured alcohol cleaning and re-lubrication with a trace of Vaseline will usually fix this type of failure. There are 3 springs in this unit and none of them should be shortened or stretched out of shape, there is a delicate balance between the lever springs and the retract spring on the toothed wheel hub, making one of them stronger will adversely effect the others. Cleaning always fixes binding or sticking problems... modifying the original design by tweaking the springs usually results in wrecking the unit.

Payout Unit Service - Payout Disk
The payout unit consists of a contact disk (5) with a wiper (6) which is rotated from contact to contact by the toothed wheel (7) which is advanced by the step-up solenoid (1) and reset by the reset solenoid (2).

Only the step-up solenoid has an "end of stroke" switch (3), a second switch group (4) is present and referred to in original schematic diagrams as a 2nd STEP switch but I think it's more appropriate to call it a "start of rotation" or a S.O.R. switch.

The big difference between this payout unit and the odds unit is that the contact disk does not have individual contacts but instead, it has concentric rings which act like a continuous contact and they have cuts in the rings at various places to denote different payout amounts. Unlike the odds unit which counts up to the maximum amount of coins deposited as it occurs, the payout unit normally sits at it's fully reset position and only when a payout happens, it counts up (counter-clockwise) to the amount of the award. This seems backwards but it makes perfect sense considering how the pay boards in the reel assembly interface with these units.

A payout unit also has only 50 positions, so with some award amounts, more is needed. Multipliers used in conjunction with payout units can increase the range of the disk by the multiplier counting 2,3,10 or whatever and then actuating the payout unit once. The hoppers coin switch will now have to actuate multiple times for the payout unit to move once, turning 2 coins paid out into 4,6 or even 20 or more. Amounts in the hundreds of coins are possible with the use of multipliers. In observing the payout amounts the particular game has, you will notice multiplier relationships in these amounts.

Maintenance for this unit is basic dusting or wiping with a damp rag moistened with denatured alcohol. Many problems in payout, coin handling plus lighting and display can often be traced to this unit. Bad contact continuity being the most prevalent. Removing the wiper and bending the contact fingers down a bit can increase the contact pressure. A good cleaning with T.V. tuner cleaner/lubricant works wonders and even possibly some contact burnishing can alleviate contact problems. Don't forget about the switches, they get dirty too and a good wipe and burnish can bring them back to life as well.

One last potential problem is the unit not resetting fully. This is caused by too much friction in the rotating assembly. The way to fix this is to disassemble the unit enough to remove the toothed wheel. Once removed, a good denatured alcohol cleaning and re-lubrication with a trace of Vaseline will usually fix this type of failure. There are 3 springs in this unit and none of them should be shortened or stretched out of shape, there is a delicate balance between the lever springs and the retract spring on the toothed wheel hub, making one of them stronger will adversely effect the others. Cleaning always fixes binding or sticking problems... modifying the original design by tweaking the springs usually results in wrecking the unit.

Logic Relay
These relays are the general purpose logic elements for the slot machine. There are 5 in the Triple Choice, 5 in the Triple Pay and 10 in the 8 Ball Special. These relays are used for cutoff, impulse, jackpot, start and pay functions as well as miscellaneous logic gate functions. Each relay is identical, they are all 48/50VAC coil 4PDT (four pole double throw) relays. Several manufacturers parts are used throughout the production run of slot machines, most of which are not available any more.

Service - GPRelay
48/50VAC 4PDT RELAYS (08/01/2005)
Manufacturer Part No. Availability
Omron MY4-AC48/50(S) Available from Mfg.
American Zettler 1309-4C48A no longer available
Cornell-Dublier 104A0-48 no longer available
Omron MY4-UA-AC50 no longer available

These relays are not really serviceable except to replace them when they go bad. The main failure with these relays is burnt contacts. Although the contacts are rated for 250V, some of the 115VAC circuits can cause some sparking when the relay is actuated causing a blackening of the clear relay case in places. A dark spot on a relay case does not necessarily mean the relay is bad, a check of the relay contact with a multimeter will sort out any problems.

*** NOTE ***
Since the beginning of the digital revolution, 48/50VAC components have fallen out of favor, being superceded by digital TTL,CMOS compatible 12VDC or 5VDC components. Today manufacturers make 48/50VAC components only sparingly because no one really orders them for building new products.

Coin Relay
The coin relay is a dual action relay with a 4PST(4 pole, single throw) and a 4PDT (4 pole, double throw) switch configuration. This relay is more complex than a standard relay because it has one relay coil to snap the contatcs in one position and another to reset the position.

Service - Coin Relay You can manually actuate the odds rotary stepper switch and then manually set this relay to make the slot machine operate from the handle without having to put a coin through the coin mechanism. Granted that you will have to have the reel cover up and the equipment drawer extended to do so, but this is an easy way of testing and troubleshooting the machine.

It should be noted that the coils used in this relay are "Bally G31-1800" coils and operate on 48/50VAC. It is uncertain if the entire mechanism, or just the Bally coils are manufactured by Bally. Maintenance for this unit is to simply dust and clean with a damp rag moistened with denatured alcohol.

You may want to burnish the contacts with 600 grit sandpaper but do this sparingly and only if absolutely necessary. Contacts are plated with a hard conductive metal like rhodium which is microns thick. Excessive sanding can remove this coating causing the contacts to corrode quickly. It is best to attack the contacts with some alcohol and cotton swabs or even T.V. tuner cleaner/lubricant before considering sanding the contacts.

Multiplier(s)
Multipliers are solenoid switches that close every n actuations, for example: a 2X multiplier (times two) contacts will close ever two pulses to the solenoid, and X3 would be every three and an X10 would close every ten effectively multiplying the number of input pulses by their number.

Service - Multipliers There are two types of multipliers used in these slot machines: the multiple multiplier (left) and the X10 multiplier (right). The multiple unit has X2, X3, X4 and X5 but only X2 and X3 are used. If these were 5 coin games, then the X4 and X5 multiplier would become useful.

The X10 unit on the other hand has only 1 multiplier circuit in it. This multiplier is used 3 times in the 8-Ball Special game and has a bright yellow number wheel attached to each. These X10 multipliers are involved with jackpot payouts $100.00 and up.

Multipliers are used to expand the range of payout units which typically can not count past 50, and more realistically, not beyond 30 so for amounts of hundreds of coins, these multipliers come in handy.

All solenoids in these units are 48/50VAC and the contacts are good for 250VAC, although, lower voltages are typically used. Maintenance for these units is basic dusting or wiping with a damp rag moistened with denatured alcohol. Some problems in payout can be traced to this unit. Bad contact continuity being the most prevalent.

Variator
Time for a little history... In the late 1940's it was found that slot machines (strictly mechanical then) could be persuaded to give up their coins in greater than fair amounts with a special handle jogging technique of which popular books have been published in the early 1950's like "How to Beat The Casino Slots". This prompted the Nevada Gaming Commission to require a new device in slot machines named a "Variator" which added random (in reality, pseudo-random) delays to the reel spin process. This seemed to solve the problem, so from then on, slot machines required a variator. Service - Variator

Fast forward to the 60's and 70's with the advent of electro-mechanical machines and a variator now becomes a useless appendage on the machines because the player no longer has a direct mechanical link to the reels, everything is controlled via microswitch. The electro-mechanical reel assemblies behave very random and technically do not need a variator at all to assure fair random play. Never the less, variators remain a piece of required (if redundant) equipment.

The variator used in the A.C.M.E. slot machines employs two different motor driven cams each with its own microswitch. The 115VAC motor is geared to put out only 2 RPM. The black plastic disc is the variator and has unevenly spaced features... this suffices for randomness. The white disk is actually used to pulse the jackpot horn and has nothing to do with adding random delays to the handle pull. The action of the black disc produces a variable delay when the reels are spun. The white disc pulses the jackpot horn.

The only problems that can arise with a Variator is if one or both of the microswitches are bad or the motor is bad. Both of these occurrences can be fixed by replacing the faulty component. For all practical purposes, you can simply jump around the variator all together and experience no tangible difference in the play of the slot machine. Of course, jumping around the white disks switch will cause the jackpot horn to blast continuously until a jackpot is completely paid out. If the motor is bad and you are jumping around the variator disks switch, make sure to leave the horn pulse disks switch open to avoid the annoying continuous drone of the horn when you hit the jackpot.

Timer
The timer is the device that shuts the slot machine off when too much time has elapsed without any action. This usually happens when the coin hopper runs out of coins. If you are familiar with electric lawn sprinkler timers you will be right at home with this one because, that's kind of what it is.

Service - Timer Although the machine is shutoff by the timer, it still remembers where in the cycle it was so when more coins are put in the coin hopper and this timer is deactivated, the remainder of the coins will payout. This is not a reset timer, it simply stops the action if a time lag happens which is interpreted as some sort of fault.

This timer operates on 115VAC and rotates at 1/2 RPM. The rotating lever at the top can be positioned to give delays from 6 seconds up to 104 seconds. 30 seconds is usually enough time to determine if your slot machine has a fault. Pressing the black button halts the slot machine, pressing the white button on the other side start it back up. You can use this button to stop and start the machine during troubleshooting.

Maintenance for this unit is basic dusting or wiping with a damp rag moistened with denatured alcohol.

Test Rig
To properly test and debug problems with these slot machines a test rig was needed. As far as I know, there may have been a similar unit at ACME back in the day but any remnant of such a device was long gone. I needed to make one from spare ACME slot machine parts, video game and pinball machine parts and some pieces of particle board. This rig tests the reel assembly, coin hopper assembly, coin acceptor and general purpose relays. It can test all of these removable items simultaneously and was a vital piece of equipment in the restoration of these slot machines.

The following three pictures give an overview of it's construction and use.

Service - Test Rig 1 Service - Test Rig 2 Service - Test Rig 3

One of our customers was given this rig when they purchased one of the last ACME slots after restoration operations were completed, so, this custom piece of electrical marvel is now amongst the missing, I hope they did not scrap it, that would be a shame.

-William Stephens (C.E.O. So What Software, Inc.)

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