As you’ve discovered for yourself, the bonus unit’s operation on JJ/JitB is a tricky timing orchestration of the score motor and several relays. My Jumping Jack had intermittent problems like yours, with endless iterations of the bonus stepper. It got worse in the winter, and better in the summer. I’m guessing contraction of the switch stacks during the dry winter months meant a switch somewhere continued to “make” when it shouldn’t.

Right now Jumping Jack is in the shop, getting a deep restoration. I’ll be swapping in a new playfield within the next two weeks. Once that is done, I will have to troubleshoot the inevitable bugs. If your problem persists until then, I’ll see if I can offer any insight based on my findings.

Because there are ten drop targets, the score motor has to make two 120-degree turns to tally the bonus for all the targets. It does this via pulses at level A on the score motor. Level A has five teeth, so 5 pulses × 2 turns = 10 drop targets.

Relays E and F appear to have a complex interdependency on the schematic. I’m thinking they’re staggered/offset such that one or the other ensures the score motor can make exactly two 120-degree turns for bonus scoring.

It got me to wondering about cam wear on level C of the score motor. A couple of the “valleys” on my Jumping Jack have a bit of an indent from friction when the switch dog hitches down. This would cause any switches on C to prematurely open or close, and that could affect timing on the dance between E and F, and maybe cause an infinite loop.

Do you see any cam wear on the C level of your Jack in the Box’s score motor?

C-Level Cam Wear

That “cryptic notation” in the circuit for the O Relay means when the bonus unit’s wiper board is at the zero position. Along with the runout switch, it’s another key position for this unit.

I could be overthinking things with the wear on the cam. Gottlieb probably engineered the timing of this bonus unit operation with forgiving tolerances. Other owners would have reported such an issue before us. Over 13,000 JJ/JitB games were made.

Still, this tricky circuit has piqued my curiosity. I took the score motor sequence chart and doubled it for two 120-degree turns. Maybe it will be helpful to you.

Jack Score Motor Sequence Chart

Is the O relay doing anything when you close the outhole switch and the bonus unit is cycling endlessly?

Here is what the zero position looks like. The two sets of wiper fingers closest to the runout switch bridge the orange and green-white wires. They’re annotated as 1 and 2 respectively. Their order looks backward, but that’s because the orange wire has a jumper wire over to the left-most rivet under the wiper board.

Zero Position

But you are absolutely correct. Your zero position circuit must be working because the ball kicker actuates when you take your finger off the outhole switch. O has to energize for that to kick, and O needs a functioning zero-position connection.

Additionally, O can only energize when F is enaged and closes one of its switches, but then O simply holds itself through its own closed switch. Taking your finger off that outhole switch somehow makes that circuit through F work. So something about the outhole switch closure is causing F to not be engaged when the bonus unit reaches the zero position.

The O relay is probably engaging only momentarily while the zero-position circuit is complete, but then the bonus unit keeps stepping, breaking the zero-position connection, which means O drops out and the ball doesn’t kick or the drop targets don’t reset. But that path through F is working for a split-second to engage O. That’s good.

E is what relays motor pulses to the bonus stepper, so it is imperative E is not engaged when the bonus unit reaches the zero position, so O can do its work. For some reason, E is remaining engaged at this critical juncture.

Here is something you can try: remove the nylon switch armatures for both E and F. Look for a worn spot on the metal plates that is the shape of a half-moon. This is caused from the armature rubbing against the coil. Over time, the opening/closing of the relay (and 60hz vibrations) create a slight impression on this plate. When the coil loses power and the relay disengages, this indentation can introduce friction that makes the relay hesitate before letting go, which is just enough to mess with timing-related operations.

It can be an incredibly marginal happenstance, and circumstantial factors can make this hesitation come and go. Moving the game vibrates and shifts its mechanical contents—ever so slightly—causing this indentation to start/stop affecting the relay’s operation.

You can smooth out this impression with rotary tools. NicoVolta uses a flapwheel on a Dremel. I’ve found that a stiff wire wheel works, too.

The F relay on my Jumping Jack does not have that orange jumper wire. That isn’t the only difference. This is likely explained because of the different wiring needs for 2-player vs. 4-player, so somebody with another Jack in the Box will have to compare.

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This advice just won’t get you anywhere. My Jumping Jack is in the shop and the playfield is out of the machine. Actuating the E relay causes an infinite score motor loop because the O circuit through the playfield is permanently disconnected.

I recommend removing the entire insert panel (“score motor board”) and putting it onto a work bench. A seasoned EM tech can lean into a cabinet and dismantle/reassemble a relay, but it’s a risky procedure the first handful of times you do it.

This is a bit tedious because it involves detaching all the wires from the chime unit, the knocker, and both switches on the side of the cabinet. The good news is these connections slide off, so no soldering is involved. The power switch and tilt assembly (mounted on the side) must also be unscrewed and removed with the main board.

But really, it takes less than ten minutes to extricate. Once it is out of the game, on a flat working surface, with good light, you can really see what you’re doing.

This video by @newmantj shows you how to deal with the relays you’ll be working on.

Incidentally, I wouldn’t do everything Todd does in this video. Don’t bother with putting the assembly in an ultrasonic cleaner or polishing all the contacts with a Dremel. You just need to get those nylon armatures out, inspect the plates for wear, sand them smooth, and reassemble carefully so the switch stacks are screwed down tightly and there is good, solid make-break action.

One thing to watch out for: the coils in your Jack in the Box have a washer between the base of the coil and the inside of the enclosure. The game in this video (Jacks Open) uses a different type of coil that doesn’t need a washer.

Be mindful of their order when reassembling. Look at your other relays for reference.

Those dirty half-moons you saw could also mean somebody smeared some grease into that relay. You might be dealing with the compound effect of (a) dirty and solidified grease, (b) armature plate wear, and (c) possibly some residual magnetism. Add them all up, and it’s easy to see how that “E” relay (my bet it’s the culprit) could be failing to disengage in a timely fashion. Your results experimenting with the return spring tension bears that out.

It feels like you are on the verge of a breakthrough. Good luck disassembling those relays.

P.S. I take it back about cleaning the relays; you don’t need to give them an ultrasonic bath, but try a citrus-based degreaser to get rid of that old grease. Also, give the armature plate a couple whacks with a hammer to knock out any residual magnetism. I’m doubtful there is any, but it doesn’t hurt.

As for your new problem, the manual has a very detailed breakdown of the startup sequence of events.

https://user.xmission.com/~daina/tips/pub/tip0480.html

Based on that, where do you think things are breaking down for you?

There’s another place for potential wear on the armature, and that’s the fulcrum point in the rectangular cavity. It can get excessively worn and interfere with normal make-break operation. Also, the coil itself could be retaining some magnetism.

Replacing the armature plate will definitely ameliorate any issue with a worn fulcrum or magnetism in the plate itself. NOS armatures are in good supply at PBR and Marco, from what I understand. Make sure you order the AC version.

If the coil contains residual magnetism, that can also be replaced, but soldering would be involved.

Oh, since you mentioned you can get E to release in a more timely fashion by futzing with the spring: you could make some adjustments to the blades that go through the nylon ladder slots. The spring does most of the work returning the armature plate fully to home when the coil loses power, but the tension of the blades going through the ladder perform some assistance. You can add additional tension with judicious adjustments so they’re pushing the nylon ladder just a little more. This is called “biasing,” and frankly it’s kind of an unorthodox technique. Gottlieb engineered their coils, springs, and armature plates (all of a certain rating) to work in concert. Replacing the plate is the best long-term fix.

I hunkered down tonight and scrutinized this torturous circuit. I used Photoshop to triple the score motor chart, making it represent one full 360º turn of the motor. This is because the motor needs to turn 270º to tally all the drop targets, then another 180º turn for O to do its business of kicking out the ball.

F’s job really seems to be keeping E offline after starting the business of bonus scoring. F could be dropping out at the spot I’ve identified, which makes E rear its ugly head again.

Jack Bonus Timing Circuit

I see you have been spending your time tonight doing the exact same thing. How funny.

I wish I had done this sooner. There’s a luxurious amount of space between the operations of these three relays. Even if E were “hesitating” to unlatch because of mechanical/magnetic issues, there’s still a lot of tolerance in how the timing was engineered. Had I tackled this diagram first, I wouldn’t have recommended you do all that work on the E relay armature. Sorry about that, but I hope it was a fun learning experience for you.

You’re observing that F is dropping out as soon as O engages, so that means its other dependent switch at score motor 1B is not doing what it should. It’s an NC switch, and it probably has too much oxidation and/or the contacts aren’t closed tightly enough.