That is fine. The other connection for the green would be to the transformer frame.

https://pinside.com/pinball/forum/topic/replacing-line-cords-plugs-wall-sockets-vids-guide

I tried to find this on the schematic, but didn't spot in the few min I looked at it.

What's the strip made out of? It almost looks like metal? Or is it an insulating material?

Can't tell by looking, but if it's metal, it would be a place for making ground connections. Seems odd that all those various colored wires would be ground. If it's insulating material, then probably a convenient place for testing those various circuits and missing a wiring label.

I was thinking the exact same thing on both your comments. Seems like an expensive way just to measure a test point, plus I didn't spot anything on the schematic that resembled a test point terminal strip. But only owned one EM, so not much experience working on them.

If you look at the schematic there are basically three main busses. I would imagine it is the one on the left (top) of the schematic.

https://ipdb.org/machine.cgi?id=1735

I see two things in the picture of note.

1. That row of tie points may be something of benefit to the manufacturing process, but not intended for operator use. I've never seen a LABELED strip of tie points in an EM game.

2. That washer that got loose inside the cabinet and landed perilously close to where it could short out the line-voltage tie points. If there are loose metal parts around, I'd suggest putting some kind of insulated cover over the hot connection. For example, you could take the clear plastic shield normally used on a coin switch. When you move the lower cabinet on a hand truck, loose metal parts land in unexpected places.
.................David Marston

That strip is a feature expansion... One can see two punch marks for a relay assembly to be inserted and incorporated into the existing wire harness... Extra coin feature? Extra ball feature? I do not know.

Distribs of that time might discourage variations, but it was possible for operators buying games new from the factory to specify how many coin chutes were installed and what pricing (and coin entry plates and acceptors) would be set up as the game was being built. Each game going down the line would have its own ticket to specify pricing options. This could affect the presence or absence of a "second chute relay" or "third chute relay" on the main relay board. Other manufacturers would also have an optional relay for 2-coins-1-play (for two nickels in the USA or Canada), but Williams accomplished that in a pure mechanical way. I think this supports @vec-tor's theory about coin/pricing related optional relays.
.................David Marston

Definitely not a ground plane. My understanding of a ground plane relates to the rf world. Essentially as I understand it a ground plane is a “spring board “ if you will that an rf signal uses to get out in the atmosphere. If you’ve seen a cv antenna on someone’s home or an amateur antenna you may note there are sometimes, depending on the antenna three horizontal elements and one vertical. The horizontal elements make up the ground plane. In a boat that may have a SSB radio, the ground plane would be comprised of a copper screening material that is laid inside the hull and then connected to other “grounds” like tanks, engines really anything metallic to comprise the ground plane. Probably more than you wanted to know!

I'm a RF design engineer(but don't design antennas, I design transmitters - what connects to the antenna). At my printed circuit board (PCB) level, it's really as simple as a ground that is considered to be a low impedance ground at RF frequencies. Could be a copper layer on a PC board, maybe a metal backer plate that is part of a PCB, a slab of metal that's also a heatsink, etc. A ground trace is usually inductive which represents a high impedance to RF...so not a good RF ground. Same with a wire, it's really an inductor. That's why in the RF world, quite often an entire layer of a PCB is copper, not traces. Plenty of other reasons to have a ground plane tho. For example, a ground plane might simply be used as a heatsink for a part - not RF.

That's sort of a generic explanation. But like everything, it can get complicated.

But since this isn't a newer pin, there's no RF. Just 60Hz (excluding a transient generated by a solenoid firing). So ground, even if thru a wire, is considered 'ground'. Interestingly, the newer Sterns with the metal backbox? Those are really EMI shields. Essentially a grounded case (i.e. a shield) which helps contains the high frequency digital signals which are really RF. Sort of like a ground plane, but being used as a RF shield instead. Used to pass FCC testing.

Hope I didn't derail the thread too much. Just thought I would toss out a simple explanation.

O/T: Did you know that on a clear cool evening you can put your fingers on just the right capacitors
to a Bally S&T snd board and pickup radio stations.

Not sure if you're pulling my leg or not...but I almost believe it! LOL

Can you answer my question? On my Bally Rolling Stones, when the ball hits either slingshot (and it activates), for a split second I hear a noticeable very HF sound. I tried to record it to play here, but you can't hear it on a recording....either because it's too faint, or because it's higher than the recording device can detect. It's not in my brain, there is a definite HF sound when that circuit is energized. None of my other early Bally SS do that. What could be causing that sound?

Hey Jethro, I'll PM you later so we don't derail the OP's topic. While I design RF, far more smarter people here than me when it comes to pins, so take anything I say w/a grain of salt! Technically correct?...hopefully I'm right. Real life experience from fixing pins for 40 years?...nope, not me.