Here’s what I would do to test -

There is a pair of switches to the left of the 5 (in front of the 8 ) and another pair to the right of the 5 (in front of the 9). One switch in each of those pairs should drop the 7. If none of them drop the 7, then see A below. If one of the switches in each of those pairs drops the 7, then see B below.

A. Either the 7 relay coil is bad, or there is a switch on the relay that is normally closed (to arm the coil) and opens when the coil is fired (to keep it from burning out). If that switch is open when the 7 is lit, it will prevent the coil from firing, and therefore prevent the 7 from dropping.

B. The coil is good and you have a connection issue between the 7 alley rollover switch and the coil. Not necessarily the switch itself.

I’ve read that Bally bowlers are known for having terrible connectors. If the pin relays are in the back box, then there is a connector between the alley switches and the relays. So, if you determine that the coil is good and the de-energizing switch on the 7 relay is good (normally closed), then a good bet would be on the connector.

Your problem peaked my curiosity - especially the part where the 7 relay fires as part of a combo with the 4 but not with the 7 switch. I thought that ruled out an issue with the 7 coil, but I don't think it does. I have a United bowler from the same era but I think the wiring is probably quite similar if not the same. The relevant parts of the schematic are inserted below.

The switch arrangement matches your Bally with the exception of 2 extra switches that allow the player to accomplish a 7-10 pickup as a result of a SDTM split. They are labeled 10B (next to the 7) and 7B (next to the 10). We can ignore those switches.

As you can see, there is a stand alone 7 relay that drops the 7, but there is also a combo 4-7-8 relay that also drops the 7. So, if the 7 gets dropped as a result of the 4-7-8 combo switch as you mentioned, that just means that the 4-7-8 relay is good. Now... we know that the 7 switch does not fire the 7 relay. So the next move would be to see if the 7A switches cause the 7 relay to fire. As mentioned before, these switches are located to the left and the right of the 5 pin. Moving the puck down each of the strike corridors will test them. If the strike corridors both drop all the pins including the 7, then your issue is with a wire/connection between your 7 switch and the relay. If they don't drop the 7, then it could be the coil or the aforementioned relay switch (shown in the schematic as the normally closed (NC) 7 RE switch just above the 7 coil). It could also be a wiring issue between the coil and where the 7, left 7A and right 7A switches come together. That would require some wire tracing on your part and even the correct schematic probably wouldn't help you much there. If the 7 coil and 7 RE (NC) switch were determined to be good, I'd start cleaning the connectors.

Switches:
switches (resized).jpg

Relays:
relays (resized).jpg

OK. Looking at the schematic, just pressing 7A (the one you are pointing at) by itself should not do anything. It will only fire the 7 relay if the switches in front of it have also been pressed. In other words, it needs to be part of the strike corridor sequence. Anyways, sounds like you ran the puck down each corridor and the 7 pin remained standing, so the next thing I'd check is the 7 coil and switch on the 7 relay that I mentioned that must be closed when the relay is reset (7 light is on) and opens when the relay is fired to de-energize the coil. If that switch is always open, the coil is always de-energized. Do you have easy access to the 7 relay/coil with the game powered on? Can you post a picture of it? Also, can you find a relay/coil labeled 4-7-8 somewhere in the mix?

Since it is likely that there is more than one switch on the 7 relay, the switch I am referring to will be the one that is wired directly to one side of the coil. If you need help testing the switch and the coil, let me know and I can suggest a few things without physically swapping another coil in there.

I have circled what I presume to be the 7 pin "relay assembly". Each pin has a relay assembly as well as the combos "5-8-9", "4-7-8", etc. Each relay assembly consists of a series of switches and a small coil. The large coil that you see resets all the relay assemblies to start a frame. When one of the smaller coils is fired, the arm that is holding the switch leafs up (on that pin) is released, toggling the switches. If you look under those switches, you will find the small individual coils for each pin. You should be able to rotate that entire switch bank up to better inspect the switches and the coils. Typically there is a wing nut or something on the end of the bank that releases the mechanism in order to rotate it.

First thing is to carefully inspect each of the switches on the 7 pin relay. One of the switches will have a wire that connects directly to the coil. That is the switch that must be closed and making good contact when the bank is reset and will open when the coil is fired.

If that switch is making good contact, then the problem is likely with the 7 coil. I'll make a post explaining my suggestion for easily testing the 7 coil in a bit.

bowler_relays (resized).jpg

Each pin coil should look something like this.

s-l400 (resized).jpg

When energized, it becomes a magnet and pulls a small metal plate towards it. The plate will only move 1/8"-1/4". When the plate moves, the arm that is holding the switch leafs up is released and pulled down with a spring.

OK, if the switches look good, then next thing is to inspect the coil and the mechanism around it to see if it looks and functions like those around it.

To test the coil:

If at any time you hear buzzing, power off the game immediately. It means that one of the coils is being energized because of a stuck switch.

Each coil has two wires soldered to it. One of the tabs is connected to a switch related to that coil's relay. We are concerned with the other tabs. The ones that are not connected to the associated relay switch. They should be connected to the switches on the alley. WITH THE POWER OFF, use a small length of wire to connect the tab on the 10 coil (the one that doesn't goes to the relay switch) to the tab on the 7 coil (the one that doesn't goes to the relay switch). Now, power on, reset to a new game, and press down the 10 switch on the alley.

The 10 pin should drop and so should the 7. If the 7 doesn't drop, then the 7 coil is probably bad.

You shouldn't have to remove the individual switches at this point. The whole bank can be swiveled up. Look for a nut, wing nut, or cotter pin on the end of the bank. With that removed, the entire bank will swivel on some hinges.

I'll be back in a bit.... Need to clear 2 feet of snow off my driveway.

Hmmm. I guess Bally doesn't make it easy.

I have 2 ideas. The first is to see if the entire bank of switches can be lifted at the same time. Refer to the attached pics - the switches all screw into the angle bracket (A). If you remove the screws on each end (1) will that entire bank lift off?? (be careful of the switch on the right end).

If that doesn't do it, then you might have to remove the entire assembly - the four nuts labeled 2. In that case you'd also have to loosen the wire harness clamps as well.

1a (resized).jpg

2a (resized).jpg

Pay attention to the brackets (for lack of a better term) that are intermingled within the switch leafs. If they aren't also attached to bracket A, then you'll have to take some pics to make sure it goes back together correctly.

Can you tell if all the coils are attached to bracket A as well?

Your pictures don't show the area on the back side of the switch bank (where all the wires are soldered to the switch tabs). I was thinking that if the coil tabs are accessible (under the switch solder tabs), you could at least determine that the problem is definitely the coil before you go through the trouble of disassembling the switch bank.

Just to reiterate, the coil test I described is only valid if the switches on the 7 pin relay are determined to be correct and working.

If you are unsure what I am getting at, a picture zoomed in to that area of the 7 and 10 switches may allow me to elaborate.

Well, to ensure you get the correct coil, you will first need to acquire a schematic. Another possibility is to email PBR and if you describe which coil you need and the name of the game you need it for, they might be able to help you out. As a last resort, if you can't find a schematic or get info from PBR or someone else, then you can measure the coil voltage at the transformer and if it is 26-30 VAC, then that coil from Marco that you linked to is probably a good bet.

I'd still try to figure out a way to test the 7 coil in place before you go through the trouble and expense of buying a new coil and pulling that bank apart to replace it. It would suck to go through all that only to find out the problem is with a switch or connector and not the coil itself.

1. Does one or two of the wires from each stack of switches go down to the coils below?
2. Can you access the solder tabs on the coils without removing the entire switch bank?
3. Have you tripped the metal plate on the 7 relay to make sure that the relay works physically, and thereby also checked the function of the switches associated with the 7 coil/relay?

Since you can't get access to the coil tabs, you'll have to figure out the wiring so you can attempt to fire the coil another way.

How about my previous questions 1 & 3?

Also, its sounding like removing the switch bank by removing screws (#1) might be a can of worms, especially if those switch actuator arms don't come with it. To access the coils, you might need to remove the entire assembly via screws #2 plus the wiring harness clamps. That should take the switches on the ends with it.