Transporter the Rescue, Pinball Machine (Bally, 1989)

Symptom: Machine is not working at all
Location: Greenwood Village, Colorado

The first problem the machine had were the batteries had been forgotten about. So the battery holder was replaced and new batteries were installed. All too common a problem.

While replacing the batteries, I noticed some burned circuitry.

Burned circuit in one of the pop bumper driver circuits

The burned driver circuitry was related to the lower pop bumper. Whenever I see this kind of damage, I always check the fuses.  Sure enough someone installed a 7 amp fuse where it should only be a 2 amp fuse.

Some of the fuses in an Williams System 11 pinball machine.

Out of the 6 fuses shown above, 3 were incorrect values, all higher than what they should have been.

The fuses are meant to protect against this kind of damage. Often in the history of a pinball machine, someone will replace a fuse with a higher rated fuse to keep it from blowing again without every investigating why the fuse blew in the first place. I’m not really sure why people do this. So instead of just simply having a blown transistor, the circuit board got damage and the pre-driver transistor, 7402 chip, and the coil were all damaged and had to be replaced. The 7 amp fuse never blew to protect the circuits.  Instead the transistor caught fire and burned until it acted as its own fuse and the circuit eventually opened.

The actual cause was the switch contacts on the pop bumper being adjusted too close together. Causing the pop bumper to energize continuously.

This wasn’t my customer’s fault. The blame probably goes to the operator who first purchased the pinball machine and placed in a public location to make money. A fuse or two probably blew and to keep the machine making money, installed larger fuses. Then eventually the pinball machine ends up in a home environment with the wrong fuses installed.


The Lost World Jurassic Park Pinball Machine (Sega,1997)

Symptom: Snagger releasing ball too early, or not lowering enough to grab ball.
Location: Lakewood, Colorado

The snagger mechanism on a Lost World pinball machine uses both optos and microswitches to determine the ends of travel.  Or more accurately, the microswitches are wired in series with the motor to cut-off the power when at one end or the other. The game MPU has no knowledge that this has occurred. The MPU instead uses the optos to determine when it is at one end or the other. So the microswitches are acting as safety switches to stop the motor if the optos fail or are unplugged, etc. The game code also has a timer to flag an error and disable the snagger if it doesn’t reach one end or the other in the allotted time.  When using the special test function in the Diag->Lost menu, the display will show the status of the optos, but relies on the switches to stop the motor at one end or the other. But during game play, the optos are used. So adjusting the switch levers had no effect.

Over time, the gears and belts develop mechanical play or slop. The original designer never accounted for this. The only adjustment is the center of travel, basically the flag that interrupt the optos. This can be loosened, rotated, and re-tightened on the motor shaft.  One could also loosen one of the pulley screws and accomplish the same thing. But this only adjusts the center of travel. If I adjusted it so that the ball would release and fall into the Jeep properly, the snagger wouldn’t lower far enough at the other end to grab the ball. If I adjusted it to grab the ball properly, it wouldn’t raise far enough and the ball would release on the edge of the Jeep and just sit there.

The largest source of play is the cam on the left side of the last hinge of the snagger.  As of this writing, Marco Specialties sells the shaft and the end housing of the snagger.  I wasn’t able to remove the last pulley due to damage of the set screw, so replacing it wasn’t an option.

What is really needed is a way to move one of the optos so that the motor runs a little bit longer to account for the slack in the mechanics.

I removed one of the optos and with a very small Dremel bit, created slightly curved slots for the opto leads in the circuit board. This would allow for the opto to be adjusted.

Showing new position of opto before final adjustment in the machine.

Added wires to leads to allow for movement

After determining the ideal position for the opto and adjusting the center travel (as mentioned above), I put a little drop of hot-glue on the top side of the board at the end of the opto to hold it in place.

The snagger now works perfectly.  Not the prettiest solution, but sometimes things need a slight design tweak. If there were more Lost World machines out there, I’d design an aftermarket board that would make this a lot easier.

Wizard of Oz Pinball Machine, Jersey Jack (2014)

Symptom: Version 2.0 LED Board replacement project
Location: Parker, CO

The Wizard of Oz (WOZ) pinball machine was state of the art back in 2013/2014.  There were many things about it I admired, the biggest standout were RGB LEDs used everywhere including the lowly general illumination. Previously pinball machines had fixed colors for their lights.  On this machine every LED can be individually controlled to be any color.

However, with time, the lighting system has proven to be problematic and there were several attempts at making it more reliable. It’s one of those problems that didn’t become apparent until machines were built and out in the real world. Many people suspect the problem is static electricity building up and damaging the LED driver chips.  (I think the root problem is the Allegro LED controller chip is not very robust, especially its serial output drivers.)

There are now 4 generations or versions of light systems for this pinball machine. The first three are all controlled with a serial signal that passes through a long chain of LED controller chips.  If any chip in the chain fails, it causes all the other LEDs downstream to function incorrectly.

  • The original system used in machines built prior to September, 2014, is often referred to as “5 volt unbuffered”.  This is the least reliable system.
  • There is a later system referred to as “5 volt buffered”, where the serial control signals are buffered with a driver chip.  I was told by a person who works at Jersey Jack Pinball that this is the most reliable of the serial systems.
  • There is another referred to as “7 volt”, which uses a 7 volt power supply rather than 5 volt. The serial control signals are also buffered.
  • And finally there is the “Version 2.0” system, which uses an entirely different LED control scheme and is the system used on newly built Wizard of Oz machines, as well as The Hobbit and Dialed-In.

My customer has a machine that was manufactured in September 2014 (the date of manufacture can be found on the rear of the machine), and it contained mostly 5 volt unbuffered light boards.  There were probably at least 3 boards failed, including some of the large ones.  Given there were no replacements available for one of the large boards, we decided to upgrade the machine to the Version 2.0 system. What follows are some tips to anyone who is upgrading to the 2.0 system.

This was one of the early 2.0 upgrade kits (ordered in January 2018) and some things mentioned below may have changed/improved in the later kits.  I was warned it would require over 20 hours for a novice to do the upgrade. With my experience working on pinball machines, I was able to do it in 10 hours with assistance from my customer. (This was working straight through without a break. If I do it again, I’d split it across 2 days.)  The machine was an Emerald City Limited Edition (aka WOZ ECLE).

There were 11 pages of printed instructions provided with the kit. Initially the instructions are pretty concise with photos. There are variations in the way the machines were produced, so sometimes you have to connect the dots and deviate from the instructions.

The most time consuming aspect of this project is each GI or single RGB LED board has different mounting holes than the original boards.  There are about 30 of these total, which translates into positioning, marking and drilling pilot holes for the new mounting screws on all three playfields.

One of the inaccuracies that became apparent was that there were two different lengths of #4 sheet metal screws (SMS) provided in the kit (1/2 inch and 3/8 inch), but only the 1/2 inch length is referenced in the instructions. This caused me to run out of screws later in the project. The correction here is that the 1/2 inch screws are used to secure the large boards to the playfields, and the 3/8 inch screws are used to secure the 2-holed, single RGB boards to the playfields (the boards without the bracket or the nylon spacers).

About half-way through the project the instructions were becoming less concise.  One of the big annoyances was the kit included no brackets for mounting the new power supply to the back of the cabinet. The instructions say to use a standard “L” bracket, as if everyone has those lying around. We didn’t, and it would have been an hour round-trip to the nearest hardware store.  My customer had recently repaired a chair with some 1 inch “L” brackets, and we stole those from the chair so the WOZ upgrade could continue. The other related error is they say to use an 8-32 by 1/4 inch machine screw to secure the “L” bracket to the power supply. The mounting holes for the power supply are metric, and fortunately I had some metric screws on hand.  An M4 x 6mm would be a good size to use.

Talk about lazy… how hard is it to include some hardware to mount the power supply to the cabinet?

Another problem that surfaced towards the end of the project was the cables for the single LED boards were too short. The instructions don’t give suggestions regarding the orientation of the single RGB LED boards around the inserts. I positioned them in a way that made it easy to access/drill the new holes, but in a couple of cases, this positioned the connector further away from the controlling board.  To anyone doing this, I recommend orienting the single LED boards as shown on page E24 in the WOZ manual.

Which brings me to another point about the instructions. A number of places the instructions reference another set of instructions contained in the Wizard of Oz Operations Manual. This is especially true towards the end of the project. In this day and age of Copy and Paste, why couldn’t the relevant sections be included in the 2.0 upgrade instructions?  It would have been a lot easier to work from one document rather than juggling two (or in my case, juggling printed instructions with an iPad).

In spite of trying to get the project completed in a day, in the end, the upgrade kit was missing a cable.  So it will require another visit to install the missing cable, tidy-up and install wire ties to the new cabling, and test. But I consider the project 98% completed.


Revenge From Mars Pinball Machine (Williams, 1999)

Symptom: Would not boot up.  Machine appeared dead.
Location: Littleton, Colorado.

Revenge From Mars is one of two pinball machines using the Pinball 2000 platform, which combines pinball and video. A video image is projected down onto a special playfield glass which merges video action with pinball.

The pinball machine is controlled by a customized personal computer platform. The machine uses a CRT for the video projection. Both the PC and CRT have many failure points.  Parts to repair the PC are scarce, as are people who can repair CRT monitors.

This particular pinball machine had been upgraded to an LCD monitor and a modern PC.  The PC was running software provided by Nucore, which allows the custom Pinball 2000 system to be emulated on commonly available PC hardware.

Pinball 2000 Nucore system

After checking some voltages, it appeared power was going into the PC, but nothing was happening beyond that point. So I ordered a new power supply and installed it, and it was still dead. I was expecting to have to replace the PC motherboard.  As a last ditch effort, I decided to check the CMOS memory battery. The battery was dead, but I had never encountered a PC that wouldn’t power up due to a dead battery.  I replaced the battery and surprisingly it powered up.  Most PCs will still power-up with a dead battery, but you get a message from the BIOS saying there is a problem with the CMOS (or NVRAM), and it often hangs before booting the operating system.

Coin battery for CMOS RAM

The motherboard is a Foxconn A6VMX series.

Once the PC was powered up, I had to go through several settings in the BIOS and change their default values:

Power State: Power ON
Halt On: All Errors But…
Keyboard: Enabled
Mouse: Enabled
Floppy: Enabled

Under Peripherals:
The parallel port mode should be EPP
Address: 378

The above settings will allow the system to start as soon as power is applied, and will skip checking if the keyboard, mouse and floppy are present.

Once the system was booting up, I discovered a number of switches and lights not working.  I replaced a couple of switches that were broken and adjusted the ones that weren’t working. For the lights, every one of the light boards had cracked solder joints at the input connector, which often resulted in the entire board not working. This is a common problem on most late model Williams machines using circuit board mounted 555 bulbs.


There has been some legal drama surrounding Pinball 2000 emulation systems.  Nucore developed the system, but were found violating the GPL open source license. At around the same time someone removed the copy protection and distributed the Nucore software for free as Pinbox.  Nucore and Pinbox are the same thing. Nucore is back with an updated version, but currently without the licensing to make copies of the original pinball 2000 ROMS, which are required to run the emulation.

Moving a Pinball Machine?

One of the questions I get asked the most is how to pack up a pinball machine for moving. There are several different approaches, depending on whether the head (backbox) folds down with a hinge or not. Generally, pinball machines made after the mid-1980’s have a hinged backbox.

Hinged Backbox (machines newer than mid-1980s)

  1. Remove all loose items from inside the machine such as the ball(s), coin box, manuals, everything!  Some machines have an option in the test menu to eject all balls from the machine.
  2. Open up the backbox and remove any large bolts holding the backbox to the neck of the cabinet.  Some of these bolts might look like a large wing-nut.
  3. Close up the backbox.  Make sure the inner door is closed and latched tightly, so it doesn’t rub on the backglass.
  4. Unlatch the backbox.  On a Bally/Williams machine, this might look like a suitcase latch.  On Data East/Sega/Stern, you will need to insert a large Allen wrench into the hole on the back and rotate it.
  5. Carefully pull the backbox towards the front of the game, while ensuring the cabling between the lower cabinet and the backbox is not getting hung up on anything.  There should be enough slack in the cables to allow the backbox to rest on top of the playfield portion of the lower cabinet.
  6. Note where the backbox is being supported by the lower cabinet. Place some cardboard, Styrofoam, towels, or other padding material in between to keep both the lower cabinet and the backbox from damaging each other.  This is usually at the very top of the backbox and the edges of the lower cabinet. Do not lay any packing material that would put pressure on the backglass.
  7. With straps, rope, or plastic stretch-wrap, tie or wrap the backbox to the lower cabinet so that the backbox can’t be lifted off of the cabinet.
  8. Place a chair or your knee under the rear of the lower cabinet and remove the rear legs, by removing both bolts in each leg.
  9. Lower the rear of the cabinet to the floor and then stand the pinball up on end so the coin door is facing up.
  10. Remove the front legs by removing both bolts in each leg.
  11. Keeps all of the bolts, balls, etc., in a safe place so they don’t get lost.
  12. With the machine on end, a dolly/hand-truck can be used to move the machine.

To reassemble the pinball machine, just reverse the process.

If you are shipping the pinball machine to another location, Contact NAVL (North American Van Lines) as they seem to have quite a bit of experience shipping pinball machines.

Detachable Backbox (machines older than mid-1980s)

  1. Remove all loose items from inside the machine such as the ball(s), coin box, manuals, everything!
  2. Open up the backbox. Label and disconnect the electrical connectors between the backbox and the rest of the machine.  On an EM machine there will be 2 or 3 large connectors.  On a solid state machine, you will either have to disconnect the plugs from the circuit boards (Bally), or there may be in-line connectors in the neck of the cabinet (Williams and some Gottlieb) that will need to be pulled apart.  You may leave connections that just go from one part of the backbox to another.
  3. Remove the 2-4 large bolts holding the backbox to the neck of the cabinet.
  4. Close up the backbox.  If you have a solid state machine, make sure the inner door is closed and latched tightly so it doesn’t rub on the backglass.
  5. Lift backbox from the lower cabinet.
  6. The power cord can be carefully stuffed down into the neck of the machine.
  7. Place a chair or your knee under the rear of the lower cabinet and remove the rear legs, by removing both bolts in each leg.
  8. Lower the rear of the cabinet to the floor and then stand the pinball up on end so the coin door is facing up.
  9. Remove the front legs by removing both bolts in each leg.
  10. Keeps all of the bolts, balls, etc., in a safe place so they don’t get lost.
  11. With the machine on end, a dolly/hand-truck can be used to move the machine.

To reassemble, simply reverse the procedure.  Take care to put the power cord back into the notch (this varies from machine to machine) before setting the backbox back onto the cabinet. Also take care in reconnecting the connectors to their original locations.

Note: Some people like to treat detachable backbox machines as they would a hinged backbox, by leaving everything connected, laying the backbox facedown on the lower cabinet, and securely wrapping or tying the backbox to the lower cabinet, as if it had a hinge.  But you need to make sure the backbox doesn’t move at all, so that it doesn’t pull on the wires (plastic stretch wrap would be best for this). This might be desirable if you are shipping a machine. But if you are moving a machine, it might be easier to move it as two pieces.


F-14 Tomcat Pinball Machine (Williams, 1987)

On F-14 Tomcat pinball machines, there is a light board mounted on the right side of the back wall of the playfield.  This light board holds the 6 flashers that are under the red (or white) domes.  Almost every F-14 Tomcat pinball machine I’ve worked on has had a damaged light board.

Original F-14 Tomcat light board with broken sockets.

Original F-14 light board, with damaged circuit board traces and someone’s attempt at fixing them.

The Williams part number for the circuit board is 5768-12151-00.

After searching around for an after-market replacement, and not finding one, I decided to design and make a new one.

New replacement board by Peak Pinball at the bottom.

The new board features #906 wedge type sockets with “L” brackets for support, beefier circuit board traces, repositioned connector and LED type flasher bulbs. I installed the new board into my customer’s machine and it worked perfectly.

I made some extra prototype boards.  If you are interested in purchasing one, contact us.  The price is $60 including USPS Priority Mail shipping in the lower 48 states (the price will be higher to Alaska, Hawaii, and international), and it includes red LED flashers and mounting hardware for the rear of the playfield. I only have a few boards available, and I don’t currently have plans to manufacture more.


Space Mission Pinball Machine (Williams, 1976)

Symptoms: 50 or 5000 points repeatedly scoring.
Locations: Denver and Fort Collins

I’ve worked on several Space Mission pinball machines over the past 3-4 years. One problem they’ve had in common is the sometimes the 50 or 5000 point relays will get stuck and stay engaged.  The problem would often go away when I raised the playfield, making it very difficult to diagnose.

The 50 and 5000 point relays are mounted on the underside of the playfield in the upper left corner (lower left when playfield is raised and viewed from the underside).

The problem is the main wiring harness which comes onto the playfield on the right side shorts against the bracket holding one of the stepper units. Over the years repeatedly raising and lowering the playfield causes the edge of stepper bracket to wear through the insulation on some of the wires in the main harness.  The stepper bracket has voltage on it via the main Yellow power supply wire. This creates an intermittent short between the Yellow supply wire and whatever wire(s) on the outside of the harness which happen to have their insulation compromised.

The symptoms are variable with the most common problem being the 50 and 5000 point relays staying on.  But I’ve seen other symptoms including hitting the center target when the 5000 point lamp is lit and not scoring and not scoring bonus points at the end of the ball. One machine had 3 wires that were occasionally shorting against the bracket which caused constantly changing symptoms, most of which would go away when the playfield was raised.

The fix is to remove the stepper unit near where the harness attaches to the playfield and then remove the screws holding the harness clamps. Wrap the harness with several layers of electrical tape near where the bracket is. Then reattach the clamps and the stepper unit.

I will try to remember to take some photos next time I work on a Space Mission and update this post. Often the last thing I’m thinking about when I’m at a customer’s working on their machine is taking photos of what I’m doing. A picture is worth a 1000 words.


Junk Yard Pinball Machine (Williams, 1996)

Symptom: Randomly kicks out balls into shooter lane.
Location: Arvada, CO

When playing the machine, occasionally a ball would be kicked up from the ball trough and then launched into play.  This would happen mostly during multiball when an additional ball wasn’t supposed to be launched, but I witnessed it once during single ball play.

There are a couple of automatic functions working regardless of the state of the game. The first is when the Trough Eject opto is blocked (switch 31 on the matrix), the machine software will kick up another ball from the trough. The second is when a ball is sensed in the shooter lane, and it’s not the initial ball of the turn, the ball is auto-launched into the playfield. So, a false signal on the Trough Eject opto during play will cause a ball to be kicked up from the trough and launched into the playfield.

After checking that the optos were functioning properly and reflowing some solder joints, the problem still existed.

After playing the machine some more, the owner discovered it was related to the flippers.  Intense flipper use would cause a ball to be ejected and launched.  This also explained why the problem was more prevalent during multiball, because the flippers were being used a lot more.  This is very similar to the WPC flipper reset problem, but instead of reseting the machine, it would kick out another ball.

We were able to verify this in the Switch Edges test. Hitting both flippers at the same time would cause the column of optos, switches 31-37, to momentarily go away (with no balls in the machine).  At this point, the problem was easy to reproduce.

Power portion of 16-Opto Switch Board Assembly

The signals for the optos are processed by the 16-opto Switch Board Assembly (A-16998). The board is powered by the unregulated +12V supply circuit from the Power Driver Board. The oscilloscope revealed that the +12V power was dipping during heavy flipper use. This was expected since it’s not regulated. However, on the Opto Switch Board, there is a diode (D19) and a filter capacitor (C6) to filter out transients and dips in the supply voltage.

The important part of the circuit is the Vref (reference voltage) generated by R52, 100K and R31, 22K. This signal shouldn’t have a lot of variation or electrical noise. But the oscilloscope revealed it did.  My first choice would have been to replace C6, but I didn’t have a suitable replacement with me. But since Vref is the most important, I added a 22uF capacitor across R31, the 22K resistor.  This fixed the problem.

This same circuitry is used on the 12-Opto Switch Board and the 10-Opto Switch board (and probably others) used in other Williams pinball machines of this era. The component designators are different on the other boards, so look at the schematic for the matching circuit as shown above. Look for the power coming into the board and going to a diode.  If you’re having this problem, replace the main capacitor (C6 in the diagram above) and if that doesn’t help, add a 22uF capacitor across the 22K resistor.


Old Chicago Pinball Machine (Bally, 1976)

Symptom: None of the lights working.
Location: Superior, Colorado.

One of the most common repairs I do is related to burnt connectors for the lights on a pinball machine.  Most of them are on solid state machines built by Williams and Data East. But even an EM machine can have this problem.

Burnt lighting connector from Bally EM pinball machine.

Unlike the newer machines where new connectors can be installed, the old ones require a work-around. In this case, the connector was between the control board plywood with all of the relays mounted on it and the fuse block on the right side of the cabinet near the tilt mechanism.  This is a little used connector which would only be used if one were removing the control board from the pinball machine, which is pretty rare. Most EM pinball machines don’t even have this connector, so I had no problem just splicing the bad wire together and bypassing the connector.

Had it been a connector for removing the backbox or playfield, I probably would have installed a single pin Molex connector or something similar for the bad wire.

Since the lights on this machine hadn’t worked in years, there were a few tune-up related items that needed to be done, such has replacing burned out bulbs and cleaning some relay and stepper contacts to get all of the lights working again.


Wurlitzer P-10 Jukebox (1934)

Symptom: Effects of time travel
Location: Denver, CO

The P10 was Wurlitzer’s first jukebox.  The repeal of prohibition in December 1933 led to the opening of many public drinking places and live musicians and jukeboxes were the primary forms of entertainment.  Wurlitzer and other jukebox manufacturers were quick to capitalize on the repeal.

Advertisement for the Wurlitzer P10 (click for larger).

This jukebox was found in the old Denver Hardware building that was slated for demolition. The owner was able to purchase it for approximately $100. The owner contacted me to determine what was needed to get it working.

Although the cabinet was a little rough, the amplifier and mechanism seemed to be largely untouched. It looked like once it stopped working, no one had tried to fix it and it just sat for decades. The internal counter says it played 40,000 records in its life.

Once I got the mechanism unfrozen and lubricated, I discovered the motor was burned-out. Many electric motors of the 1930s and 1940s didn’t have protection circuits to shut the motor down if stalled or stuck. I later discovered a 15 amp fuse in the 6 amp fuse holder.

Motor with rear casing removed. Note the inner layer of windings which are charred.

Close-up view

Quotes to rewind the motor were in the neighborhood of $700.00. I was able to find a motor on E-bay which came out of a Wurlitzer 412 for $80, so we decided to give that one a try first.

Motor purchased on E-bay was poorly packaged and arrived with broken wires and styrofoam pieces inside of the motor.

I had to take apart the motor I purchased on E-bay to repair it.  I installed a fuse on the motor along with new wiring.  Hopefully the fuse will protect the motor in case the jukebox mechanism jams.

Motor ready to be placed back into jukebox.

The next item was to check the amplifier.  It was missing two 2A3 tubes, but fortunately they are still being made in Russia and China, and I was able to order a pair.  The capacitors in the amplifier needed to be replaced.

Dry electrolytic capacitors in a cardboard box.

Once the amp and the motor were reinstalled (and the correct fuses installed), the jukebox fired up and played a record.

Jukebox playing one of the records that was found in it. Note the original needle.

The needle and sound system was kept original and it sounded good.  Now the only thing it needs is a cabinet restoration, which I no longer do. But I know some cabinetry people who can do this.

Wurlitzer P10