Category Archives: Pinball

The Games Pinball Machine (Gottlieb, 1984)

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Location: Brighton, CO
Symptoms: Pop bumper not working, display digit not working, needed cleaning and tuneup.

The machine was good condition.  I should have taken photos because the photos in the IPDB are of a machine in very poor condition.

The non-working pop bumper was simply a broken wire going to the coil. I resoldered it.  I checked the other pop bumper switches and noticed the top bumper’s switch was sticking.  If you press down on a bumper skirt and it doesn’t immediately pop back, you’re asking for a burned-out coil.  I cleaned the spoon that the bumper skirt rests on and that seemed to help a lot.  Often the pointed end of the bumper skirt that contacts the spoon gets roughed up and needs to be sanded or filed smooth and round again.  It’s a pain to do because it’s difficult to get to, and often involves removing it which requires taking the whole assembly apart.

The display on Player 3, least significant digit, was dead. I checked the card edge connector and made sure the card edge was clean.  I fired-up the oscilloscope and saw that the pulses (4 volt) were going into the digit driver IC, but no 60V pulses were coming out of the pin for that digit.  The other digit drivers within the IC were working fine.

The IC is a UDN6118A, which is no longer made.  These can the purchased used on E-bay from Chinese distributors. There was also a new one available at a US chip broker, for $15, plus $8.99 shipping.  Does it really cost $8.99 to ship something that weighs as much as a paper clip?  No!  For the same price, I can get 5-10 used chips from China.

For the time being, I swapped the Player 3 and Player 4 displays because the owner said the Player 4 gets used less often.  The owner is contemplating whether to repair the display or live with it.  I was surprised to see that PinScore doesn’t make aftermarket displays for Gottlieb (and neither does anyone else that I could find).

I also advised the owner that the rechargeable battery on the System 80A control board should be replaced before it leaks and ruins the circuit board.

I replaced bulbs and did a quick cleaning of the playfield.

When I played the game, I thought the sound board had something wrong with it.  There was a lot of background noise.  But it turns out the background noise is supposed to be crowd noise like at a stadium.  I verified by watching a YouTube video of the same machine.  You have to use your imagination.  I think it would have been better to have some background music with an Olympic theme.

 

Space Invaders Pinball Machine (Bally, 1980)

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Location: Near Morrison, CO.
Symptoms: Blows fuse (F4).

The machine would immediate blow the fuse (less than 1 second) upon powering up.  Fuse F4 supplies the 43 volt solenoid circuits which are prone to broken wires, shorted coils, etc.  So, I expected to find a short somewhere on the playfield.   I isolated the power supply by removing all of the connectors except for J2 (cabinet) which supplies the wall AC power to the power supply, but this connector also supplies solenoid power to the knocker and the coin door.  The fuse still blew.  I checked the cabinet wiring to make sure there was no short, then focused on the power supply itself.

It turned out to be a shorted bridge rectifier between the AC and the minus (-).  I brought the power supply back to my shop for repair.  I looked up the part number for the bridge and found it on Marco’s site.  For better or worse, the bridge I received was slightly larger.  Not only were the pins further apart, it was also thicker.

New bridge rectifier (black square) above an original working bridge rectifier just below it.

This posed a problem as there are two bridge rectifiers in the circuit and both are mounted on the bottom side of the PCB and are heat-sinked against a metal bar on the power supply chassis.  If one is thicker than the other, one will be heat-sinked, the other will not.

I decided to shift the bar over, so that existing bridge would contact the bar and the new bridge would go directly to the chassis.

With the metal bar, both rectifiers will contact the chassis when the board is remounted.

I added some new heatsink grease to both bridges.  I powered the circuit and all was fine.  This power supply was only used on two machines, KISS and Space Invaders.

Back at the customer’s location, the game powered up and worked fine.  I replaced a few burned out bulbs.  The NiCad RAM backup battery mounted on the CPU board has partially failed. I am debating whether to replace it with a 1 farad super cap, or the typical 3 cell AA holder.  The super cap requires the machine to be powered up periodically so that it can recharge.  The AA batteries don’t require recharging, but there is no nice place to put the battery pack and they have to replaced every few years.

 

Funhouse Pinball Machine, Williams (1990)

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Location:  Greeley, Colorado.
Symptoms:  Many.  Bulbs out, trap door not working, a pop bumper not working, both sling-shots not working, flipper sticking, etc.  Needed general servicing.

The biggest mystery with this machine was that every GI (General Illumination) bulb was burned out, except for 3.  I suspect that at some point in the past, there was a GI short to a solenoid supply which blew most of the bulbs.

As I was replacing some of the controlled lamps, I discovered some that were burning very brightly.  This raised a red flag that one of the rows or columns in the lamp matrix was stuck on.  The easy way to check this is to go into the test menu and run the single lamp test.  If more than one light comes on at a time, then the row or column driver is shorted or bad.   It turned out to be Column 8 and the TIP107 transistor.  All of the Column 8 lamps would light when any of the other columns were on.  After replacing the transistor, the controlled lamps all worked except one.

The one lamp that didn’t work was the “Open Trapdoor W/Flashing” light.  It was lighting when any other column or row was lit. In other words, the only time it acted normal was when any thing in its own column or row was lit. At first I thought it was a shorted diode.  The diode tested OK with the meter.  But the meter doesn’t test the diode at greater than 3 volts.  So I snipped it and the light should have gone dark, but it didn’t.  It turns out, someone had soldered the wires onto the socket incorrectly and bypassed the diode.  Once I corrected the wiring, it worked fine.

As for the sticking flipper, it was a bad link that was catching on the end of the solenoid.  I replaced the links, plungers and rubbers on both lower flippers.  The upper flipper looked good enough to leave alone.

The other solenoid problems were all related to broken wires.

The trap door wasn’t working because the end of the spring broke on the solenoid that latches it up.  I found the spring in the bottom of the machine and made a new hook with my pliers, and reattached it.

The game had an L4 version Game ROM (U6) installed.  The most recent official version is L9, plus there is an L9.05H, which is a home version with some additional features.  The difference between and L4 and L9H requires a move to a larger ROM (1 Mb to 2 Mb), plus one of the sound ROMs (U18) had to get upgraded to L3.

The L9H ROM images I downloaded from ipdb.org didn’t really match the documentation.  The U6 ROM image was a 4 Mb image, and U18 was a 2 Mb image.  In this Funhouse machine, both of these parts were 1 Mb so I couldn’t erase and re-program.  I was out of 2 Mb EPROMs.  So I ordered some blank 2 Mb parts from Marco and received 4 Mb parts instead. Ugh!  I looked at the schematic for the sound board and saw that it would support a 4 Mb ROM.  So, I programmed both images into 4 Mb EPROMs.  This works fine for U6, but for U18 it doesn’t work without loading the code into the upper half of the EPROM to make it look like a 2 Mb part.  Although the sound board hardware supports the 4 Mb ROMs, the firmware in the other sound ROMs doesn’t.

A note on CPU jumpers for larger ROMs:  I think by default, the early WPC games had the W2 jumper installed.  W2 supports the 28 pin ROM families and will still work with a 1 Mb 32-pin ROM because the associated pin on the 1 Mb ROM is not used.  But anything larger (2 Mb or greater) will need the W2 jumper removed and the W1 jumper installed.  The W1 jumper supports all of the 32-pin ROM families.  So when using a 1 Mb ROM, the jumper can be in either position.

The same is true for the sound board with regards to U18.  Jumper W4 supports the 28-pin families and jumper W3 supports the 32-pin families, with the 1 Mb ROMs not caring which position the jumper is in.  But keep in mind that at least for Funhouse, the sound system firmware doesn’t support anything larger than a 2 Mb ROM in U18.

After correcting dozens of small problems, the pinball machine is looking and working great!

Haunted House (Gottlieb pinball machine, 1982)

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Location: Wellington, Colorado.
Symptoms: Would blow fuse as soon as ball landed on lower playfield.

The problem was obviously a short related to something that powered the lower playfield.  I inspected the wiring and coils on the lower playfield and didn’t see any issues.  With the machine off, I checked for shorts in coil and flipper power wiring and didn’t see any.  I finally found the short with my meter in the playfield illumination wiring, and it turned out to be on the main playfield.

On the underside of the main playfield, there are 8 lamps that light the lower playfield. These lights only illuminate when the ball is on the lower playfield, and are controlled by a relay.  Next I did a visual inspection of each of the 8 lamps, and as usual, found the short on the last one I checked. 😉  The center contact was shorted against the side of the socket, which is typically where lamp circuits short out.

The owner had replaced all of the lamps with LEDs.  One important thing to note:  On Haunted House and Black Hole, these 8 illumination lamps are powered by 28 volts, which will blow out regular 6 volt LEDs.  The original bulb number is a #313. You either have to use an LED specified to replace a #313 bulb, or you have to modify the lighting circuit to operate on 6 volts (a procedure is here).

 

Star Trek: The Next Generation (Williams pinball machine, 1993)

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Location: Littleton, Colorado.
Symptom: Left cannon/gun shooter wouldn’t find its home position.

This one had me stumped for a while.  If I executed the diagnostic test for the gun shooter, it found the home position normally, without fail.  Yet when powering up/booting the game, it just cycled back and forth.   I checked and adjusted everything associated with the home microswitch.  I finally concluded there had to be a bug in the firmware.

It turns out I was partially correct.  There is an optical sensor located at the front of the gun to sense when the ball is in position and ready to be fired.  If this sensor fails, the revision LX-3 firmware ignores the home switch, will not home the gun, and it gives an incorrect error message. This post helped steer me in the right direction.

I burned (programmed) a new game ROM with more recent LX-7 code.  In the revision history, there is mention of “Enhanced the broken gun launcher opto compensation.” I don’t know if it fixes the problem of the incorrect error message or not, because I went ahead and fixed the opto sensor problem.

To troubleshoot the opto sensor problem, I first checked the voltage across the IR transmitter located on the left side of the cannon. It was about 1.3 volts, and this normal. Next I checked the voltage across the phototransistor located on the right side of the cannon.  It was reading zero volts, with or without blocking the light beam.  A properly working sensors would have approximately 12 volts across it with the light beam blocked, and between 0 and 1 volt with the beam unblocked.

Next, I checked the continuity through the wires down to the first connector under the playfield.  It turned about both wires were bad.  I noticed that the shooter solenoid wires to the gun had previously been replaced as well. It is a common problem that flexing wires thousands of times will break them.  I suspect they are broken where they go through the playfield.

I ran two new wires from the phototransistor down to the connector and left the old wires in place. That fixed all of the problems.

ST:TNG is one of my favorite pinball machines in terms of theme execution.  The audio clips are great and integrate well into game play.

Twilight Zone Pinball Machine (Bally, 1993)

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Location: Littleton/Denver, CO.
Symptoms:  Flipper problems, ROM checksum error, Proximity Sensor error.

I started with the ROM checksum error.  I re-seated the game ROM in U6 and the other socketed parts, with no improvement.  I programmed a new 27C040 with the game code (decided to try the 9.4H version) and replaced the ROM and the problem was solved.  I verified the code in the old ROM and there were several bits that had reverted back to 1, which was causing the checksum error. This probably caused the game to lock up occasionally, which was one of the complaints.

The proximity sensor senses when a normal metal ball is delivered to the shooter lane (as opposed to the Power Ball which is made of ceramic).  It was simply out of adjustment and not located close enough to the ball to sense it.

The flippers had the most problems.  Neither of the left flippers were working properly.  The top flipper was kicking out, but not holding and the bottom flipper was vibrating and buzzing and weak.  At first I thought the two problems were related and that there may have been a driver problem on the Fliptronic board.  But that wasn’t the case.

The upper flipper had a broken wire on the holding coil. I resoldered it the coil and it solved that problem.

Fliptronic I Flipper Button Opto Board

The lower flipper had a more difficult problem to find.  I hooked the oscilloscope up to the flipper driver output of the Fliptronic board.  It was rapidly pulsing off and on.  When I disconnected the flipper connector, the problem went away and there was steady power to the connector.  I checked the coil resistance and found no problems.  It turned out to be the flipper button opto board.

Normally when pressing the flipper button, the optical path opens and the phototransistor begins pulling the signal down to ground from 12 volts.  When the voltage falls below 5 volts, it triggers the flipper driver via the processor.  A good opto circuit will pull down to below 1 volt.  This was only pulling down to about 4.8 volts, which was too close to the threshold of 5 volts.  When the flipper engerized, the ground probably shifted a little causing the circuit to think the voltage had risen above 5 volts, thus shutting the flipper off. As soon as the flipper shut of, the voltage would fall back below 5 and energize the flipper again.  A vicious circle, which caused the output to pulse off and on very rapidly.

I tried cleaning the opto interrupter, but that didn’t help.  The opto interrupters for this board are no longer available (as far as I can tell).  The only option was to replace the board.  Great Lakes Modular offers a totally redesigned flipper button board that utilizes magnetic sensors instead of optical. The pinball machine owner opted to give it a try.  I ordered one and installed it.

The board needs to be adjusted once it’s installed.  The LEDs on the board really help this process.  However, to adjust it, you need to slide the magnet into different positions and I found it really sensitive.  Just a 1/16″ movement will cause it to go out of adjustment.  Great Lakes recommends taping the magnet after getting it adjusted.  I opted to glue it.  We’ll see how long it lasts. Once adjusted, it had the same feel and response as the right side flipper button.

 

Bram Stoker’s Dracula Pinball Machine (Williams 1993)

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Location: Broomfield, Colorado.
Symptom: Error message indicating several switch rows shorted to ground.

The owner had checked the playfield and the coin door wiring, looking for any obvious shorts.  None were found.  I suspected there was a problem on the MPU board, where all of the columns and rows of the switch matrix connect.

Lower portion of the Williams MPU board (click for larger), U20 is just left of center. Note battery holder above it.

I disconnected all of the switch connectors from the MPU. With the pinball machine in the Switch Edges test routine, I took a couple of jumper leads and a diode and connected a Row 1 with Column 1.  Instead of seeing a single switch closure, the entire Row 1 lit up as being closed.  I repeated with a few of the other rows and got the same result.  This pointed to the column driver chip U20 (ULN2804).

To be sure, I checked the column outputs with my oscilloscope. Instead of seeing a signal pulsing from 12 volts to ground, I saw a signal pulsing from about 2 volts to ground.  I checked that there was 12 volts on the pullup resistors to make sure the PCB wasn’t damaged from leaky RAM batteries.  The 12 volts on the pullup resistor was fine.  I then checked the input to U20 to make sure the upstream chip was functioning correctly.

I replaced U20 with a socket because this is a common problem with these Williams MPU boards.  I then placed a new ULN2804 into the socket.  The board was retested in the machine and everything was fine.

Fast Draw, Gottlieb pinball machine

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Location: Boulder, Colorado.
Symptoms: Pinball machine wouldn’t reset.

A machine not resetting is the most common problem with an electromechanical pinball machine.  In a way, it’s like a self-test, because a lot of things have to be working for the machine to reset.  The reset sequence is like a series of dominoes, one item affects the next item and so on.  If one item fails to reset, then the sequence is either halted, or more likely, gets stuck in a continuous reset cycle.

This Fast Draw had been not working for nearly 12 years.  And typically with an EM machine that hasn’t been used for years, it usually needs some contact cleaning, contact adjustment, and the steppers rebuilt.  This particular machine also had a broken wire associated with the reset relay.

 

Moulin Rouge, Williams Pinball Machine (1965)

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Location: Aspen, Colorado.
Symptoms: A variety of things not working.

The Williams Moulin Rouge is an electro-mechanical (EM) pinball machine from the mid-1960’s.  The owner has owned this game for over 30 years.  However, the game hasn’t been used in over 8 years.

When I first opened the machine, I saw some disconnected wires dangling from the playfield.  These were associated with the left flipper.  I re-soldered these wires to their respective places.

In the backbox, there were a couple of steppers that were sticky and needed to be cleaned.  The ball count stepper and the match stepper.  Even if a pinball machine has been set for free-play, the match stepper is important to have working.  The match stepper is used continuously throughout a game and is triggered by various switches in the playfield.  In this case, it controls various playfield features that alternately illuminate.

The machine wouldn’t power up due to a broken in-line switch that had been placed on the line cord.  I replaced the line cord, which had been previously spliced and installed a better quality switch.  Originally these games didn’t have power switches.  To turn the game off, you kick the bottom of the machine, which trips a “kick-off” switch.  To turn the game on, you press the left flipper button.  Kicking the bottom of the machine is awkward, so I prefer an in-line cord switch.

Once the machine was powered up, it was in continuous reset mode.  This is not unexpected with an EM game that hasn’t been used for a while.  A game will get stuck in reset mode when something isn’t detected as being reset.  In this case, the score reels were not being reset.  They were sticky and not turning freely.  Also, there was a dirty contact that was preventing the “100” digit to not get the reset pulses.  Once the score reels were fixed up, the game would reset.

The next thing I noticed was that the outhole wouldn’t register a ball after the first ball. Therefore it wouldn’t give an end of ball score, wouldn’t advance the ball count stepper, and therefore wouldn’t eject the ball to the shooter lane.  After checking the schematic to see what else was in that circuit and manually tripping the outhole relay, I noticed the scoring motor wasn’t indexing to its home position after either a trigger of the outhole relay or the eject relay. It turned out to be a couple of dirty contacts on the score motor bank that were supposed to keep the score motor running until it was indexed.

Next up, there were many lamps not working.  This wasn’t because the bulbs were burned out, but because the sockets and the lamp bases had corrosion on them.

Next up, the right slingshot wasn’t working correctly.  As the slingshot arm would kick the ball, it would get hung up on the playfield plastic over it.  The plastic was warped. I placed washers under the plastic to raise it up high enough so it wouldn’t interfere with the slingshot.

I replaced all of the rubber pieces on the playfield.

The left flipper needed a new bushing and was missing its torsional return spring.  The right bushing was okay, but both will be replaced on a future visit.

All in all, this was pretty typical work for a pinball machine of this vintage and the years of non-use.  People always ask me for estimates on this kind of work.  It’s very difficult because you have to start fixing things to see what else doesn’t work.  But it’s almost always in the 3-6 hour range.

Golden Eye, Sega/Stern Pinball Machine (1994)

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Location: Centennial, CO
Symptoms: Auto-launch ball shooter would not launch ball.  Lower playfield lights not working.

I opened the coin door on the pinball machine and immediately saw a coil dangling from the playfield.  It was the shooter coil and it was resting on the metal junction box.  It probably grounded out against the box causing the 50V supply fuse to blow.

The coil bracket had broken from the stresses and vibration of years of use.

The lower playfield general illumination lights were not working. I suspected a connection problem on the IO Power/Driver board.  I couldn’t find any problems with the connector. The lights started working momentarily on their own.  I could hear a faint buzzing that seemed to be emanating from the fuse.  I tapped the fuse and the buzzing would change. I removed the fuse and tested it.  It wasn’t blown, but there was a connection problem inside of it (more on fuses here).  I replaced it and the lights began working reliably.

Once the lights and the shooter coil were fixed, I played a test game and discovered a playfield ramp switch that was dangling with nothing holding it. I wasn’t able to locate any screws lying in the cabinet.  So I reattached it with a new screw.