I have a puzzling question about my 1976 Williams Space Mission circuit.

My game is not malfunctioning, I currently do not need assistance in repair. This is purely discussion of a pinball circuit.

Below is a photo of the Lock relay in my game. It's a simple break (N.C.) switch. I have also included a condensed version of this circuit from the original schematic and all unrelated circuits have been removed for clarity.

I have since replaced the burned coil in the photo.

My question:

What is the purpose of this relay? It energizes when power is applied to the machine and remains on all the time. That means the single break switch is open all the time while the game is switched on.

The only time this relay can change state while operating is if power is removed. (Game turned off or unplugged) This will cause the switch to close, completing the circuit to the GAME OVER relay trip.
The only problem with this theory is without power in the circuit, completing the circuit is meaningless.

What do I fail to understand here? Does the reverse EMF from the collapsing field in the power transformer operate the GAME OVER trip? (A guess??)

Schematic.jpg

Hi Chrisbee.

I agree. The puzzling thing here is the loss of power of a turned off game causes the lock relay to de-energize which completes the circuit to the G.O. trip coil.

But completing the trip coil circuit seems senseless without any power in the circuit.

Maybe Williams is counting on the G.O. trip to activate on power up before the lock relay has a chance to upen the circuit to ensure a game over status on power up?
Just another guess.

Thanks Chrisbee.

I had replaced the coil prior to creating this thread, and it is working properly.

I've came to... and accepted this theory helped by the others:

That since the machine was manufactured to be sold to venders to make money, this circuit will prevent the machine from re-entering in a non-game over state if the machine is powered off, then on again. If the possibility existed, the vender could loose money by someone simply powering it on by getting a free game.

Since the game over relay is of a latching type, suppose the machine was switched off in a non-game over state at the end of the arcade day. The machine(s) are switched back on the next morning waiting for eager quarters. But since the relay was in the non-game over state from the evening before, it still would remain so. And possibly vend a free game to the first player.

(The theory is) This hold circuit prevents this. When the machine is first powered on, the lock relay armature's switch will de-latch the game over relay, ensuring the prevention of a false vend.

So this circuit isn't really to prevent the machine from not knowing when the game is over, but to prevent a false vend when powered up.

Steve Young was right, the circuit is not needed unless the machine is vending games. The coil can be disconnected and the switch adjusted so it never closes.
But like you, I prefer the original configuration and the new coil looks a lot better in the machine than the one I pictured above.

Hi Ken!

Hey!
I noticed you have the same two machines as I have, the SO76 and Space mission. I also noticed you have a Stardust. This is really a coincidence.... I had almost picked one of those up a couple months back as another project machine.

How do you like it, in comparison to the So75 and SM?

Is your Stardust operational? I was mainly wondering about your opinion of it versus your SO and SO76.

"A lot of the machines I pick up are 1 step away from the dumpster, so I save them. They gave me a lot of fun as a kid so I want to give back and keep them from the parts bin. I love fixing these things more than playing them, but only by a little."

Yes I concur!

I find a lot of extra pride buying what is essentially someone's junk and bringing it back to former glory. Another pin saved from the landfill for another generation to enjoy is only a good thing.