I have heard that several copies of "Neptune" have a factory design flaw. I've played a few that seemed to be ridiculously easy to win extra balls on. I guess that's why.
I think you're on the right track because it has something to do with a missing resistor somewhere.
Ask your friend if the game was always like that, or if it just recently developed that fault.

I didn't know the Neptune had 24VDC on the playfield, very cool!

Hmm, this is interesting. I have a Neptune to go through in the near future. This level of troubleshooting is above my pay grade for sure. If I run across this issue I'm grateful you posted.

I'd be interested to hear a response from Steve if you talk to him about it. My preference to correct this issue if it arises would be one lower resistance coil if available. It's nice to know about the second coil hack though if it comes to that.

Yup. DC. Game play is quite fast.

That probably is the fix. I was discussing this with the late Steve Hansen at Pintastic several years ago. He had a "Neptune" for sale, and he showed me a resistor inside that he said was not installed on some of the games.

Very interesting. Our Neptune works as it should. Unfortunately, it’s not set up at the moment, but I could open it up if you need me to check or measure anything. I recall having series relay coil issues with another game, but not Neptune.

One crazy thought, do you have the original spec 44 bulbs in the spots that are fed via resistors? Im wondering if having 47s or LEDs could create the cheat path. I’ll have to dig out the schematic and see if anything else comes to mind. I suppose it could still be a coil that’s out of spec somewhere.

Dave

You should post this on that Goatshed facebook page: https://www.facebook.com/groups/582691718587932 (You have to join)

- John Osborne watches posts there and replies - it would be interesting to get his take on it.

I'd like to understand this better. Before the black or red series is completed, the rollovers fire one of the Rollover relays and the Series relay, right? Then when a series is completed the U or V relay trips (?) to remember that the red or black series is complete? Then after that any rollover fires the W/Wow relay?

Does blocking the U and/or V relay switches on the maroon+white wire leading to the W/Wow relay stop the Wows from happening?

I think the 10 ohm resistor in the lock in circuit is there to keep the Q/Series relay from being exposed to the full 24 volts. When the Q/Series relay fires there is a Rollover relay in series with it that takes up some of the voltage. They split the 24 volts between them so neither sees the full 24 volts. But when the rollover switch opens the Rollover relay relaxes. Without the 10 ohm resistor the Q relay would see its voltage change to the full 24 volts from whatever lower voltage it started with. The 10 ohm resistor is acting as a stand in for the Rollover relay that dropped out to keep the voltage on the Q/Series relay more or less constant.

/Mark

My old Neptune was missing the series relay’s resistor. Fortunately, a nearby friend also had a Neptune. I took some good pictures of his relay and used them to fix my game. I still have a spare resistor or two. Let me know if you want one.

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What a neat problem. Not something I've seen before. it took me a while to sort out what you meant by backfeed. To better understand what is going on I simplified the schematic:
Neptune1 (resized).jpg
The schematic above shows in red how the Q/Series and one of the Rollover relays should fire together when a rollover switch closes. There shouldn't be a path to the W/Wow relay because the stepper has selected a different rollover and is completing its path. What's really happening is more interesting:
Neptune2 (resized).jpg
This schematic shows that not only is the path to the Q/Series relay complete, but a longer path to the W/Wow relay is also complete even though the stepper isn't pointing to the active rollover switch. In the worst case any rollover will award the Wow as pinhead52 observed (once either the red or black series has been completed which closes a switch to the W/Wow relay not shown here).

Simplifying the schematic even more you get:
Neptune3 (resized).jpg
The top path through the Red 10 Rollover relay coil and the Q/Series relay coil uses coils that are intended to work together in series so that they can both operate properly given that they have to share the 24 volts between the power rails. They have very low resistance of roughly 2 ohms and can operate on about 12 volts. This works just fine until the red or black series completes and the 2nd path through the W/Wow relay is added to the circuit.

Once a series is completed what you have is the Q/Series relay coil in parallel with two other relay coils which changes the balance or the voltage that each coil sees. Even when it's working properly there is current passing through the lower path, just not enough current to fire the W/Wow relay or the Red 9 Rollover relay.

When pinhead52 shorts the lugs of the Q/Series relay the Wow problem stops (but I bet the rollovers don't score either since the Q/Series relay doesn't fire). The reason the W/Wow relay doesn't fire in that case is because the jumper essentially connects the left power rail to the junction where the two paths split. So there is no voltage difference between the left and right side of the W/Wow relay coil, no current flows and the relay doesn't fire.

The way to fix this problem and make it bullet proof would be to add (lots of) extra switches to prevent the back door path to the W/Wow relay. Gottlieb instead found a combination of relay coils that would work in the two scenarios with different voltages. After 50 years it's hard to say what changed. Maybe some of the coils were replace that slightly changed the balance?

Assuming that the W/Wow relay is using the right coil, I would experiment with adding a small resistance in series with the W/Wow relay coil. Just enough to limit the current through it so that it won't fire when the backdoor path with the two extra coils is complete, but not enough to prevent it from firing when connected directly to a rollover switch.

I much prefer the idea of a simple resistor rather than another inductive load.

More ideas for Neptune hacking in this video:

We discuss some ideas of how Gottlieb generally tried to do things the right way, starting about 40 minutes in. This thread seems to identify a situation where they got too clever.
.................David Marston

Have you tried a small resistance in series with the W/Wow relay (end of reply #16)?

Bump to help with current Neptune problem.