I'll preference this by saying that I'm newish to EMs, so this is the deepest I've gone on anything so far. (Previous experience is adjusting switches and cleaning steppers, and not much else).

When the ball ends, the bonus lights do not step down. If I use my hand to trigger the bonus stepper, then the bonus lights step down properly. Since the bonus does not run itself down to zero, this screws up the end of ball sequence.

We'll start with the easiest thing, I've not seen the bonus step down coil fire. (Aside: Looking at the schematic, I see a coil called "Bonus Reset"...I assume this is the coil I'm talking about. A little confusing since another coil is called "Bonus Step Up"...so I at first was looking for "Bonus Step Down",which isn't anywhere on the schematic.) It tests at around 8ohms. Most other coils of similar size on the machine are closer to 4ohms. Does this mean the coil is bad? I was thinking I could test it by grounding to the side rail, but either that's not working or I'm doing it wrong.

Just poked around in my nearby Prospector, which has the same coil in question (B-26 800), and it has the same ohm measurement. So, from here...

I've cleaned and adjusted the two switches in the score motor stacks called "Pulses Bonus Reset". A multimeter shows continuity when it should, and none when it shouldn't (as I spin the score motor manually). As far as I can tell, these are opening and closing at the correct moments. One thing I did notice...

On the "Impulse" wheel on the score motor, the D switch (labeled: "Pulses Bonus Reset") lists R-B-4 and BR-W-6 as the wires. Inside the machine, these seem to be correct. The brown connects over to the other switch, the D switch on the 5 wheel of the score motor. The schematic lists that as BR-W-6 and R-BLU-1. Inside the machine, the brown wire (from Impulse D) connects to one lug, which also has a Brown/Yellow wire connected to it. This is the same Brown/Yellow that connects to the Bonus Reset coil...and there is continuity there. The wire on the other lug of the switch is in the machine is Yellow/Blue.

So these colors in the machine don't exactly match up with what's the in the schematic. Maybe that's no big deal.

Anyway, not sure where to go next. Any help is much appreciated!

I should also note that the bonus relay is firing, it just doesn't seem to make progress since the bonus isn't counting down.

I discovered a switch on the Double Bonus relay that is definitely open, but it buzzes as closed. Orange/red wire coming off one side, and the other side is a green wire that connects to a switch in the adjacent Triple Bonus relay.

I see no reason why this switch is registering as closed (the wires are not touching or shorting to each other), and having trouble seeing where this is represented on the schematic, or where it goes.

Thanks for the reply. I tried to state above that I have cleaned and checked both of those switches. They open and close as they should (as tested with a multimeter and hand turning the score motor).

Bonus unit is never decrementing unless I do it by hand. Trying to figure out why.

Can you explain this more? How would you test if a switch is registering correctly then? I guess I am used to solid state where the the visual appearance of open/closed should correspond to continuity or not. That isn't the case with EMs? One of the double bonus switches that should be open is showing continuity though visually it is open.

No, it doesn't. Also, when reaching double bonus, I can see the double bonus relay flip states, but the light doesn't come on. (The bulb is good, socket just doesn't light).

It doesn't count down on triple bonus either.

Yeah, as mentioned above, it does activate.

Not in front of the machine right now, but what does this mean...how can a coil be installed upside down? I thought it was just either active or not...there was no directionality to the pull.

Also, hello fellow Boulderite @howardr!

I'm back to diagnosing this. Some interesting things...

The bonus relay does fire when you put a ball in the trough. It fires and fires and fires, but the bonus doesn't count down. However if you apply slight pressure to the relay as it fires, then the bonus steps down.

Also, if you apply pressure to the second stack in the score motor, (the one that has "pulses bonus reset"), this also causes it to step down correctly.

Me and a friend have both adjusted, cleaned, etc many times over both of these sets of switches (though, we're EM noobs).

Not asking "what's the fix" here...but I just don't understand why pressure in either location helps this move along? The second stack in the score motor in particular...a multimeter shows that the switches are opening and closing as expected.

So we switched to trying to diagnose why the bonus was not stepping down when the game started up.

...and ended up adjusting the gap between adjacent switches in the reset relay to make it larger...which adjusted the timing of when things were happening relative to other things?

Now everything kind of works.

Yay EMs?!?