Congrats! My first suggestion is get a schematic and manual. With these you can trace through the
things you mentioned one by one and locate the area of the problem.

Initially I'd focus on the drop targets. There should be a relay associated with the reset solenoid.
Its probably engaged or maybe its not and the contacts are touching. Should be fairly easy to
find that problem. After that, EMs are all about the start up sequence and it sounds like yours
is partially working right.

One thing you can do without the schematic is look at all relay and switch contacts and make
sure those that should be normally closed are and vice versa. And they move freely. Its not unusual for
one leaf of a switch to break off and be missing or floating around in the bottom of
the cabinet so do a good search there for bits and pieces.

Good luck! EMs are a blast.
Steve

If possible move this post to the EM Pinball Tech sub forum, you are more likely to get visibility to all the people that can help.

I agree with Zarcos starting advice. Sounds like there are lots of gremlins that will be fun to sort out. You have to tackle them one at a time and get them fixed. Starting with the drop targets sounds good, there should not be smoke!

Is it the Target Down relay that is locking on?

That type of interlock game over relay on these Ballys is a tricky one when you are looking at the schematic. This is because the schematic is drawn to represent the state of everything after a new game has been started, and then the machine unplugged. So the game over relay will be in “non game over” mode. But, the setup of the circuitry is designed such that when you turn the power on the game over will immediately be activated into game over mode. (This is done to account for the situation where the machine is turned off before a game has ended, which would leave “free” balls for the next player when it is turned back on). So the game over relay will actually be in the opposite position as shown in the schematic, IF you have turned on the power. It can be confusing until you sort that logic out.

OK having said all that, looking at the red rectangle shown by HowardR above, that Game Over relay switch will be NO as shown if a game has been started and then the power turned off. But, when you turn the power on, it will change to the closed position.

My first theory is that the score Motor switch 12A is not open as it should be. It should only close briefly when the score Motor turns. If it is stuck closed then that will prove a straight path for constant voltage to the drop target reset solenoid through that game over relay switch. Not good.

Luckily that should be easy to check, because the “A” versions of all score Motor switches are the ones on the top. So check the top switch on score motor position 12 and make sure it has a nice gap when the power is off.

You can get a pdf schematic from IPDB.

The way that switch is assembled, it'll be making all the time. It might be missing one insulating wafer.

I agree that doesn't look right. Here is where you get down in the mud and figure out how to work with what information you've got available. We can consult the Bally 1976 Parts Catalog (a must-have reference) and see on page 46 the detailed parts listing for the score motor of the Old Chicago. It looks like cam 12 has one switch which is part number ASW-C-10-11.

On pages 25-27 there are drawings of a bunch of different switch part numbers so you can see exactly how they are supposed to look. But that one is not shown. That part number is also not found on any score motor of the 2 similar vintage Ballys I have (Bon Voyage and Monte Carlo) so I can't look at one to compare. Nor is that same part number found on any of the other cams on the Old Chicago score motor.

Best thing to do would be to see if someone with an Old Chicago could share a close-up pic.

Now venturing into my personal theories based on your photo (nice close-up): Let's think about the function of this switch. Its job is to briefly close when the cam 12 nub comes along, thus energizing the drop target reset solenoid, and thus resetting the drop targets. The black kind of u-shaped bracket on the underside of the bottom blade will be pushed upward by the cam nub, thus closing the switch.

The top blade (flat) has an additional helper blade (bent shape) attached to it. Why is that there? My theory is that it is there to make sure that the top blade stays away from the bottom blade by physically holding it back. Because as we now know, if that switch gets stuck closed its going to energize that solenoid all the time and that solenoid is not made for that. So it is a stiff reinforcement that presses down against the bottom blade, but as jrpinball said, there has got to be an insulating piece of paper in between there! Otherwise, its just closed all the time.

You could test this I think pretty easily. You could cut a small piece of thin cardboard or card stock and wedge it between that top helper blade and the bottom switch blade, thus insulating it, and test. Or if you want to get ambitious you could physically bend that helper blade up enough so its not making contact, although that is a bit hackish (but should be reversible).

Eventually you would need to fit in a correct piece of insulating paper or fish paper as they call it. Check out this thread:

https://pinside.com/pinball/forum/topic/fish-paper-for-switches

Make sure the power cord is not damaged or a hazard.
Proceed.

Yes good advice. Also the fuses and the fuse block. That era of Bally EM is notorious for having a crappy fuse holder assembly. Do you have pic of yours?

Fuse holder actually looks pretty decent. Here's what the original one in my Monte Carlo looked like:

fuse block original (resized).jpg
Replaced it with part number FUS-HLDR-SBAP from PBR.

fuse block pbr FUS-HLDR-SNAP installed (resized).jpg

Score motor constantly running is a common problem with lots of possibilities. First question is do all of the score reels reset to all zeros reliably?

There all all sorts of switches that when briefly closed will cause the score motor to start turning. When the score motor starts turning, that switch 1D SCM on the lower left will change positions due to the shape of cam 1. It should stay closed on the right side, thus completing the circuit for the score motor, for one 180 degree rotation, then it will go back to the other side and cut off power to the score motor. So that is suspect 1, it needs to be set up right.

But also, any single one of all those other switches in that circuit, if stuck closed somehow, will give a constant voltage to the score motor and it will keep running. So you have to eliminate them all. Targets down relay, top hole relay, 500 relay, 3000 relay, 5000 bonus hole relay, outhole relay, out bonus score relay, bonus hole score relay, reset relay, coin relay, 2dn coin chute relay, 3rd coin chute relay. Ouch!

Since your manipulation of the bonus stepper stops it, maybe its something to do with either the switch on the out bonus score relay or the bonus hole score relay??

I don't know what's going on with that sling switch thing, that might be a different problem.

score motor schematic Old Chicago (resized).jpg

Wow, for a first EM you picked one of the most complex. If I remember correctly, the bonus unit is supposed to increment to zero when the ball drains, and then increment up to 1 at the start of the next ball. Sounds like the ball count unit is sticky or some such...

Looking at the Bally Parts Catalog, I think Old Chicago and Capt Fantastic were the last of the EMs, and they were building up the complexity of what they could do with EM tech. Then SS came along and changed things. Then there are also those few that floated right in between and were made as both EM and SS versions, like Night Rider, Evel Knievel, Mata Hari, and I think some others.

Yes. Bally EMs start you out with a free 1 increment of bonus.

I know you got this resolved, but I looked at my Old Chicago, and this is what my switch stack looks like. The heavy bar on mine is in the same place, but it is not bent like your photo.

IMG_7263 (resized).JPG

Thanks for posting that pic. That seems logical the way yours is. The way it was bent downward on noskills must be the result of someone making a misguided attempt at adjustment.

You can see that at the beginning of this video, when the ball comes out to the plunger, the O gets lit.

be careful with continuity. On many continuity testers, everything in the game can look like it's connected together ... because it is via paths thru coils, lamps and the transformer. It just depends on how much resistance the tester thinks is ok and still qualify as "continuity".

continuity can find open connections, but if you are looking for closed ones you need to measure the resistance or be very careful to ensure there's only one possible path between the two probe points by sticking paper between switches/under wiper fingers or unsoldering wires.

a reading below a couple ohms is a closed path, allowing for slight resistances of the probe leads, switch connections, wire lengths, etc. Anything more than a couple ohms and you are probably seeing a roundabout circuit path thru other devices.

in rare cases, a low resistance path won't work because the circuit can't carry a high current flow. e.g, if a wire is connected by a single strand, it'll measure close to zero ohms but it can't carry enough current to power a coil.

you have to measure voltages with the power on and/or use jumper wires to find some types of issues.

Score Motor switch 1D is in good order? That one is a make-break switch (also called transfer switch or Type C switch) which is referred to as the Motor Run Switch in Introduction to Bally Flipper Games doc.

I think I got my brain going the wrong way before, I am pretty sure that the score motor switches are labeled from the bottom up. So the one on the bottom will be A, then it goes upward A-B-C-D etc for however many switches are on there. And it does seem on the Ballys I have looked at so far that they put that motor run switch at the top of stack 1. In my mind I assume they did this to make it easy to check and adjust that MBB switch, since if it isn't right it can cause the score motor to constantly run.

The score motor in your pic is too far away to tell for sure, but it does look like switch 1D is the top one. I think it should have R-Y, B-W, and W wires. It should be closed between the B-W and W wires in the resting position, with the other blade to the R-Y open from the W wire. Then those will flip positions when the score motor starts turning. If the W and R-Y are stuck closed the score motor will always run. Hope all that makes sense!

1D seems like it should be OK.

I agree with baldtwit, I haven't found an ohm meter to be much help for these kinds of things. I can usually figure it out with logic, looking at the schematic, and also observing how things behave and relating them to the schematic.

The bottom line is, somehow that R-Y wire to the score motor is getting connected across to the W wire, which gives it voltage and makes it go. It could be any one of those switches in that circuit. Could it be associated with the startup? Yes, possibly. The reset relay, coin relay, and the coin chute relays at the minimum are involved in the startup. If those switches aren't staying open when they need to be it could cause this problem.

But we also have a clue from something you said before. You said if you manually hit any target on the playfield, the score motor stops, then the game plays normally. That's kind of weird, but its a clue at least. Is that repeatable? And when you do this, what happens if you hit a 500 point score? Does it score 500 properly as it should? Because that requires the score motor to make a turn to trigger the 5 pulses to the 100 point relay, and if that works and the score motor does a rotation and then stops, that shows that the score motor is working right (switch 1D).

Note that if you can observe the coin relay and the reset relay, they should energize when you press the credit button and start the startup process, then they should both deenergize back to normal fairly quickly, within a few turns of the score motor. The reset relay should deenergize as soon as all of the score reels hit zero. That actually can take a variable number of score motor turns (which are half-turns actually) depending on what numbers the different score reels happen to be on.

This might be one of those tough ones, there is a lot of weird stuff going on. There was a thread not long ago which I can't find right now, but there were similar things happening, and the problem turned out to be a shorted wire somewhere. The fact that things worked OK, then didn't work OK, points to a problem like that somewhere. Also that it sort of decided to work when the playfield was up, then didn't when it was moved. It could possibly be associated with the jones plugs also.

These are tough because its hard to nail it down with logic. It might take careful visual inspections everywhere, especially at all of the solder joints for wires at switches, solenoids coils, etc. Also checking the wiring under the playfield and in different places to make sure something isn't pinched.

There is also the possibility that there were some hacks done. The way that score motor switch was bent definitely points to someone doing a strange hack.

Its odd if the score motor is constantly running and then you trigger any event that uses the score motor, like 500 points, 3000 points, etc, it does its job, and then stops. I can't think of a logical reason it should do that.

I would however make sure the screws on that score motor stack 1 are tight, sometimes those loosen and that can cause weird behavior. And the same goes for every switch stack really.

Wow, not sure why that should happen.

Probably should go back to beginning and confirm everything is good with the power cord.

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

the game has a spinner, right?

don't ask me how many times I forget this (on the same day) ... the spinner works on gravity. When you tip the playfield up, the spinner switch may be held closed and generally screw up the game state.

if the spinner is at all sticky, lowering the playfield can leave the spinner switch closed and you get unexpected things powering.

if I notice the game has a spinner AND think about it, I usually disable the spinner switch by putting paper between the contacts.

if it's not the spinner, one approach when logic fails is to stick paper between all the possible switch contacts that can power the score motor. If the score motor still powers, you have a short. If it's ok, yank out the paper one at time until the score motor issue returns and go from there.

Thanks for posting that process of elimination. I'll try to remember it when working on EM machines.

the switch is on the coin door schematic (it's on ipdb.org). It's not needed.

wrt the score motor running, the bonus unit needs to step up once from reset position at game reset and ball drain.

when the score motor is stuck running, see if the out bonus score relay is powered. If it is, the score motor will run. Try manually stepping up the bonus unit once and the out bonus score relay should unpower ... if it doesn't, check the bonus unit zero switch with wires 30 and 54. Needs to open at step 1+.

if the root cause is the bonus unit not stepping up once, the circuit is around schem G33. Score motor 6D switch and an out hole relay switch is what should cause the bonus unit to step up.

Its definitely not unusual in this era of Ballys to see unused wires like that. Also, I swear there was a thread once where a relay was shown like yours with an installed switch that apparently has never been used. Problem is, its hard to find those threads again, even with the search function. I'm starting a new folder on my computer to put in examples of unused wiring and I'll start filling it up as I find them. This question pops up a lot.

By the colors of the wires attached to it - looks like O-G one side and BLU-R on the other.