Repair log: Solar City (Gottlieb, 1977)

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A service call turned workshop repair. This Solar City (Gottlieb, 1977) was not starting properly, nor was it working quite right when it did eventually start. Lots of work to get this machine up to scratch. Solar City is an unusual game because it shares the exact same playfield as six (!) other games. They are:

• El Dorado (1 player replay)
• Gold Strike (1 player add-a-ball)
• Lucky Strike (1 player add-a-ball for the Italian market)
• Target Alpha (4 player replay)
• Canada Dry (4 player replay, special promotional game for the French market)
• El Dorado City of Gold (4 player solid state machine made much later in 1984)

Target Alpha is the game that people generally remember as more of these were made than any of the other varieties. However, the gameplay and playfield mechanisms are basically identical between them all.

⚠️ Problems and Solutions

Game was very unsteady on its feet as the leg levellers were bent inwards at a weird angle. They were heavily rusted on. So bring out the hammer, angle grinder, spanner, lube and have a party!

The power cord was frayed and dangerous. It was replaced.

I checked the power switch at the same time and it was acting funny. When closed it was still jumping around with resistance values of up to thousands of ohms. It was replaced as well.

When turned on and the start button was pressed, the game would not start. It was stuck in a reset loop with the score motor spinning and nothing much happening on the playfield. I didn't have a manual or schematics handy while troubleshooting, which made things a little harder. Reset sequences are generally written in the game manual, but if you don't have a manual, there is some good general guidance on the reset sequences of Gottlieb games through the years on the Mr. Pinball Repair Tip Archive. There is a section specifically for two-player games such as Mustang (same year as Solar City).

This was helpful. Issues with the reset sequence are quite often to do with the reset relays. While inspecting the AX relay, I found one switch in the stack which was badly adjusted. This was a make/break switch where the main switch leaf had fallen into the wrong slot on the plastic actuator. I reseated it and adjusted it so it activated properly. Once I'd done this, the score motor stopped turning and the game (kind of) finished its reset sequence. There were still issues such as the score reels being lethargic, but those could be dealt with in the workshop. For now, a ball was now getting kicked into the shooter lane for ball 1, so we were getting somewhere.

The single biggest issue with the game was the bonus unit not counting the end of ball bonus properly, and doing it way too slowly. Most games have a bonus stepper which advances during the course of a ball. Not Solar City. It has a "scanning" bonus unit which waits until the end of the ball, then increments all the way to its fifteenth position, adding bonus points based on whether the drop target at each position is down. A very finicky mechanism, which needed a full rebuild, switch adjustments, and various adjustments on the mechanism itself. Still, very clever technology for 1977. Initially I thought this would be a quick fix. I quickly discovered that the plastic spacer on the switch stack under the unit was broken off. I glued it back into place with superglue but this didn't really improve anything. I then rebuilt the unit and gave it a good clean and lube, stripping a shoulder screw in the process. Even though the mechanism was moving nicely now, it still wasn't counting bonus correctly, or at the right speed.

I highly recommend reading this thread on Pinside by kangourou. It describes how this type of bonus unit works in detail, with pictures and extracts from the schematic. Incredibly useful for troubleshooting. I solved the first issue of a slow bonus count by adjusting the 15th position switch on the assembly. Make sure the switches are clean and making good contact, as mine were touching but not conducting enough current to register a solid switch closure.

Now the unit was working at the proper speed, I could focus on why it was miscounting the bonus. It would sometimes miss a bonus, count a bonus twice, or otherwise act a little weird. I managed to get some good slow motion video of the unit in action, which showed some of those occasions when it misbehaved. There were a couple of adjustments to be made on the assembly to tighten up its movement and ensure proper advancing and decrementing. The first was the "stop" which determines where the main cog will come to a rest when reset. This was too far forward on this unit. So when the unit stepped up for the first time, it tended to skip the first rivet on the wafer corresponding to the first drop target in the 10-bank.

The next adjustment was the step up coil. The position of the coil mounting bracket was too high, giving the plunger too much travel. It needed to be a much tighter movement so the step up armature wouldn't shake around too much. In line with this, the stop which the step up armature rests against needed fixing, too. This needs to allow just enough movement for the step up ratchet to engage the cog nicely, and more much more than that.

The credit (replay) unit required servicing. It would not increment or decrement properly.

Incrementing was disrupted by solidified grease and dirt in the pivot point for the step up coil long armature, where the pin enters the plastic bushing.

Decrementing was disrupted by a seized shoulder bolt which would not let the step down armature engage with the cog.

Entire unit was disassembled and cleaned. "Free play" mod was also carried out, by closing the >0 credit switch permanently.

Game would not always advance past player 1, ball 1. Player unit required servicing. It was a little hesitant when moving between steps, and when in the player 1, ball 1 position, it was more difficult to move. A lot of solidified grease was on the wafer and rivets.

Unit was partially disassembled and cleaned. Rivets were polished with a nylon scourer and cleaned with alcohol. Thin layer of grease was applied. Player unit switches were also checked.

Unit stepped consistently and reliably. Games would now advance from ball 1.

Drop target servicing. Many of the drop targets on this game did not fall nicely when hit. Many of them would bind or drop slowly, rather than drop quickly and consistently. These assemblies had not been serviced in a long time, so it was time to give them a clean and rebuild. There is a five-bank and a ten-bank assembly on this game. To remove them, the coil wires must be cut, or the coil housings must be unscrewed from the main assembly. Then, the switches must be unscrewed from the target assembly body. There are switches on both sides. The single switches on the rear are used to trigger scoring for a downed target. The switches on the topside are made up of two lead switches stacked on top of one another. The topmost switch controls the lamp associated with that drop target. The lower switch is used by the bonus unit to calculate which drop targets are in the down position at the end of each ball.

There's not much art or science to this part of the restoration. Just unscrew things and clean them up! The targets cleaned up nicely, as did all of the metal plates and brackets. One issue was apparent, though. The reset arm return spring was broken on the five bank assembly. This spring is necessary to push the reset arm all of the way down after it activates. If it doesn't get pushed downwards, it can hold targets up and prevent them from dropping all of the way down. The solution? Use a barrel spring on the plunger of the reset coil. Different type of spring in a different application, but it puts pressure on the same part and achieves the same result.

The small lane guide at the top right of the playfield is always smashed, because balls hit by the upper left flipper get yeeted straight into it. I decided to try 3D printing some replacements. They turned out pretty well, but are not as thick as the originals, nor do they let as much light pass through them. I'll need to experiment a bit with different print settings but I printed a couple of the larger ones for consistency and they look quite reasonable. I found the print files online (Thingiverse) however they did not include files for the larger, 2-1/2" lane guide. I made that myself based on the smaller ones. Feel free to download it and use it!

The flippers needed to be raised, as they had started to drag on the playfield. For the lower flippers, loosening of the grub screws on the shaft and raising the shaft was all that was needed. For the upper flippers, small washers were placed on top of the bushing to raise them up a tad. Very effective.

Of course, all eight score reels got a good clean and service. One of them was binding because the spring washer had been replaced with a regular washer, putting too much force down onto the reel. It was replaced with the correct spring washer.

AS (match) relay needed a service as it was not moving. It should normally move every time a 100-point switch is hit on the playfield. It was gummed up with old grease. It also needed adjustment of the switch stack as it was putting too much pressure on the ratchet, stopping it from turning.

All of the Jones plugs throughout the game were tarnished, so they were cleaned up and given a light polish.

None of the lamps on the playfield were lighting up when a game was started. The lamps were all replaced, so they were definitely good. Wiring all seemed OK, too. I checked the fuse for the playfield lamps and tested it with a multimeter. The fuse was good, but once placed in the fuse holder, there was no continuity. There was some bad corrosion on the holder, and it was no longer passing current. It was replaced.

Phew! This machine was quite a bit of work, but once everything is working properly it is very satisfying to down all fifteen drop targets then watch as the machine counts up to a massive 30,000 bonus. Game works well for the first time in years. A drop target lover's dream!