Monthly Archives: July 2014

Super Nova Pinball Machine (GamePlan, 1980)

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Symptoms: Display issues, switch matrix problems, roulette wheel problem, sound problems, lamp problems.
Location: Lyons Classic Pinball, Lyons, Colorado

I’ve been working on a couple of GamePlan pinball machines recently (Andromeda is the other one).  There is nothing particularly difficult about working on GamePlan machines with the exception of getting replacement mechanical parts.

This Super Nova pinball machine has an aftermarket market MPU board installed.  The aftermarket board uses an integrated RAM/Lithium battery component.  This is really a bad idea.  What happens when the battery dies?  It’s not replaceable without also replacing the RAM it’s attached to.  If there is anything I’ve learned in 30 years of electronics, that RAM/battery component will no longer be available when the battery needs to be replaced. This will render the board useless at some point in the future.

There was a display problem with most of the LED digits with segments that weren’t working.  This was related to the edge connector that connects to the MPU board.  Someone had added solder to the edge connector, presumably to get it to fit tighter, but it was uneven.  I took some 400 grit emery paper and sanded down the contacts so each had just a thin layer of solder.  This corrected the display issues.

This machine had several problems with the switch matrix.  You can download a .pdf of the Super Nova switch matrix here. The matrix consists of 40 switches arranged by 5 “strobes” (outputs) and 8 “lines” (inputs).

The first problem was with the Switch Catcher Unit (SCU-1) circuit board mounted on the underside of the playfield.  There are 4 switches connected to this board.  (The purpose of this board is to make sure the MPU doesn’t miss a quick hit to these switches; it lengthens the switch pulses.) When any of the switches made contact, it would momentarily short the 5 volt supply causing the machine to crash/reset. I traced this to a faulty 74279 chip.

pb-8980

Switch Catcher Unit (with faulty 74279 removed and a new socket installed)

Some of the solder joints on the backside of the connector were cracked and needed to be resoldered.

The second problem with the switch matrix was that every switch connected to Strobe #1 wasn’t working.  I traced this to a faulty connector at the MPU board.  It was just one pin that was bad.   None of the connectors used in this machine are standard Molex.  So rather than replacing only the bad crimp pin, I ended up replacing the entire connector.

Now that the displays and switches were working, I tested all of the solenoids.  The only thing that wasn’t working was the spinning roulette wheel (the Space Lab).  I traced this to a bad relay and a bad transistor driving the relay. The relay had been previously replaced with the wrong one. There was a 6V relay instead of a 28V relay. At some point the transistor that drives it shorted and burned up the coil.  After replacing both, the Space Lab wheel worked fine.

Next on the list was fixing the sound.  It was only making a single sound when playing the machine.  Usually when a machine has sound problems like this, I will check to see if there are any videos on YouTube so I can see how the sound is supposed to behave. The first thing I noticed is that there is no background sound during play.

There is a jumper on the sound board that enables or disables background sound. This was missing.  If background sound is desired, the jumper should be in the left position as shown in the photo below.

Sound Board with jumper for background sound circled.

Sound Board with jumper for background sound circled.  (Click for larger)

After installing the jumper, I was still missing many sounds. Using the oscilloscope, I check for pulses on the sound select inputs and there were none.  The problem was with the connectors at the bottom of the backbox.

Connectors at bottom of backbox.

Connectors at bottom of backbox.

At some point in the past, presumably with the original MPU board, the battery leaked and caused most of the connector pins to corrode.

Corroded connector pins.

Corroded connector pins.  The tip of the  male pin on the right had broken off.

All of the remaining problems with this machine were related to these backbox connectors. I don’t know the manufacturer of the original connectors, but I was able to find some Molex pins that worked (Male: 02-08-2004, Female: 02-08-1002). The old pins were removed from the housings using an extraction tool. Then the holes in the housings for the Molex male pins had to be enlarged using a 7/64″ drill.

Indiana Jones: The Pinball Adventure (Williams, 1993)

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Symptom: When starting game, 6 balls would eject into shooter lane.
Location: Denver, Colorado

Obviously, there was a problem with the ball trough optical sensors.  Upon closer examination, there was no +12V supply voltage on either the IR emitter side of the trough or the receiver side.

To the backbox we go.  The +12V for misc playfield sensors comes off the lower left of the Power Driver board. There are several 4 pin connectors located there (J116, J117, and J118).  All of the connectors looked good.  I checked the +12V there and it was still missing.

Fuse F116 was blown, which supplies the 12 VAC to the rectifier, which generates the DC version of the voltage.

 

Circus Pinball Machine (Gottlieb, 1980)

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Location: Loveland, Colorado.
Symptoms: Displays not working, playfield lighting blows fuse.

I was really impressed by how immaculate this machine was.  It looked like it had just been un-crated.  It definitely had low miles on it.  No doubt home-use only.

The interesting thing about the displays is that the credit/ball-in-play display was working, and the score displays were not working.  They were dark/off.  I spent a few minutes looking at the schematic, searching for what was in common with the score displays, and at the same time, not in common with the credit/ball-in-play display.  There was only one thing: the filament voltages for the display tubes.

The score displays run off a 5 VAC filament supply and the credit display uses a 3 VAC filament supply. So I started by measuring the filament voltage at the Player 1 display and sure enough, zero volts.  I lifted up the playfield and found the 5 VAC leaving the power transformer.  So somewhere in between a connection wasn’t being made.

I found the problem at a wire to wire backbox connector. In this case, there was a pin that wasn’t crimped correctly at the factory.

Crimp pin was installed incorrectly at the factory. The wire was inserted too far and the crimp went around the insulation rather than the conductor.

Crimp pin was installed incorrectly at the factory. The wire was inserted too far and the crimp went around the insulation rather than the conductor.

If I held the wire a certain way, the displays lit up.  I replaced the pin with a new one and all was good.

The next issue was that the general illumination lighting on the playfield would randomly blow a fuse.  This is usually caused by a short at one of the sockets.  I checked each socket and found one that had been damaged (right near where the prop bar is used to prop up the playfield). Just the slightest vibration would cause it to short out.  I replaced that socket and one other socket that was marginal.

 

West Slope Lubrication Tour

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Locations: Basalt, Colorado; Grand Junction, Colorado.

First stop was to work on a Wurlitzer jukebox model 1100 (1948). Like many 1940’s Wurlitzers I’ve worked on, the selector shaft and heart-shaped cam was not rotating due to lack of recent lubrication. This causes it to play one selection regardless of what was selected.  Unfortunately, it’s not an easy thing to get freed up, and takes a lot of exercising and time.

The jukebox needed some other adjustments, such as the turntable height and the clutch. I replaced the line cord because it was in very dangerous condition. The color cylinder plastic sheets were also replaced.  This was an original, un-restored 1100 in good condition.

Next stop was to work on two Williams electro-mechanical (EM) pinball machines, Grand Prix and Aztec (both 1976).  The main problem with these machines were the stepper units were not freely ratcheting up and down. This is the number one problem with EM pinball machines.  A quick disassembly, cleaning and lubrication fixes the problem.  Occasionally the spring tension needs to be adjusted.

The Aztec was missing some electrical parts, which can’t be obtained unless someone is parting one out.  But I got it working as best I could.

Next stop was an AMI jukebox, model A (1946), which is also known as the Mother of Plastic. The selection mechanism was frozen due to lack of recent lubrication.  Like the 1100 above, it took a while to get it unfrozen and moving freely.  The selection buttons needed some contact cleaning and lube (buttons would stick when pressed). The tonearm wire where it plugs into the amp needed to the resoldered.  All in all, a great sounding jukebox.

It was satisfying to breathe some new life into these old machines.