This is a half-moon credit unit, right? Have you gone over the credit unit and confirmed that it is working correctly from a mechanical perspective?

Weird things can happen if one of the drive pawls is stuck; or if either of the anti-back-turn wireforms is broken/out of alignment; or if the plastic mask wheel and the plastic number wheel are stuck together; etc.

- TimMe

I was having a hard time visualizing this with the standard wheel type, geez. yes those half moon thingys are wacky

they did not use the half moon type very long. that should tell you something.
they were overly complicated and were hard to repair. i am sure the OPS hated them

If you believe the patent docs, the reason GTB came up with that credit unit was because operators were supposedly complaining that people on location were cheating by picking up and dropping the back of the game, which was causing the add plunger of the traditional replay stepper to bounce. That would advance the credit wheel so that the game could be played for free.

In contrast, the design of the half-moon credit unit has both the add and subtract drive plungers mounted side-by-side, and they move in the same direction. If this unit is bounced, both plungers move at the same time, causing an add and subtract to occur together which leaves the credit wheel showing the same value, defeating the cheaters.

I never once saw or heard of this particular type of cheating on location. I was surprised when this unit came out, which "fixed" a problem we didn't have in the first place. (We had a lot of trouble with cheaters dropping the FRONT of the game, but that's another story).

I was always unhappy with this unit because it was so touchy, didn't hold very many credits, and frankly looked rather goofy to me. As Boilerman says, I think GTB must have had a lot of complaints about this unit because (according to IPDB) they did change back to the traditional replay stepper after Sure Shot.

- TimMe

Thanks for that write-up, Tim. You are truly an asset to Pinside (especially for EM repair and history).

i never knew why they changed it. i always thought cost cutting. they were cutting corners about this time frame.
the worst one was those @#!& particle board cabinet backs

check color codes from diagram... and swap wires...

Do you have a schematic? Can you post a snippet showing the ADD REPLAY UNIT coil and related circuitry? Also the same for the SUBTRACT REPLAY UNIT coil?

Thanks - TimMe

Just to focus on a single problem for a moment, you said in post #1 that when you start a game with the replay button, it adds a credit to the credit unit. This is clearly very wrong. Here are a couple of follow-up items related to that problem:

1. When the credit is added this way, does the knocker sound?

2. Try pulling the adjustment pins for both the 1st chute and 2nd chute, let them just hang without touching anything, and then start a new game with the replay button. Do you still get a credit added to the credit unit when you do this?

- TimMe

The bonus unit is not involved with adding or subtracting credits. If you mean the replay unit, the switches should be open when the credit window is showing zero, and they should be closed at all other times.

If the game is adding a credit and not sounding the knocker, about the only way that could happen (unless the knocker is disconnected) is if the W relay is pulling in when you press the replay button. To confirm this, raise the PF and watch the W relay when you press the replay button. If the W relay pulls in, that is a definitely a problem.

If that is what is happening, then either there is a short between the replay button wiring and the 2nd coin chute switch wiring, or someone changed the wiring of the front door and hooked up the 2nd chute coin switch to the replay button. Or, perhaps the jones plug from the front door is plugged into the bottom board socket "off-by-one", or something along those lines that would accidently cross-connect the 2nd coin chute switch to the replay button switch. I know that it's the 2nd coin chute switch that is cross-connected to the replay button switch because with all the coin adjustment plugs out of their sockets, the 2nd coin chute switch is the only one that will still be wired up to the W relay.

- TimMe

The add replay coil and the knocker coil are wired together. The only time the knocker is disconnected from the add replay coil is when the W relay is pulled in. So it doesn't make any sense for the add replay coil to fire but not the knocker, if the W relay isn't pulled in.

I certainly believe that is what you are seeing, but to me that means something is seriously out of whack with your machine. You may end up needing an experienced EM tech to go over your game in person.

As for the 2nd coin chute, that is what actuates the W relay. If the W relay is not pulling in, then my idea about the 2nd coin switch wiring was wrong.

The only other possible suggestion I have is to check all of your jones plugs on the bottom board and in the head, and make sure each plug is in the correct socket and is set correctly in the socket.

- TimMe

One other idea: Everything you have been describing makes sense if the add replay coil and the subtract replay coil have been accidently swapped, as Pinhead52 suggested in post #9. Are you sure that did not happen somehow?

For example, if you took the replay unit apart and then put it back together, maybe you swapped the coil positions when you re-assembled the unit. If you did that, you'd get the problem you are having even if you never unsoldered any of the coil wires.

Here is a quick way to check: There is a wire from one of the switches on the back of the replay unit that goes directly to the subtract coil of the replay unit. If that wire is going to the coil that is now adding credits, the two coils are definitely swapped.

- TimMe

Yep - on this unit, the coil closest to the switches is the add coil, so your unit was indeed wired backwards. The two inside lugs of the coils being tied together and attached to the black return wire is factory standard, so that part is correct.

All of these old games have been worked on countless times, so you never know what horrors you'll find when you first acquire a vintage machine. If it makes you feel any better, this is a relatively minor error compared to some of the stuff I've seen.

Anyway, it's good to know that you are putting the game back to the way it should be.

- TimMe

If you think about it...another way to set it on freeplay, it would increment instead of decrement at the start of the game Im guessing thats why they did it.

That's an excellent guess, and it also gets my vote as the absolute WORST way to set an EM on free play!

not the worst. it can be reversed with no ill effects. the hole in the coin door with a button is the one that kills me

Absolutely! I just meant it was the worst in terms of being hard to detect. Usually the free-play mods on these old games are really obvious.

- TimMe

that i agree with 100% i would of took everything in that path apart and would of never thought that the wires were swapped.
i never go for the obvious first.

Instead of adjusting the credit switch closed I will sometimes solder a jumper wire across the solder tabs of the credit switch on the credit unit. This can be easily disabled by cutting the jumper wire. And I try to make it obvious that the wire is there.

I picked this up from a guy here in the KC area that both operated and sold EM pinballs when I first got into the hobby 20 years ago. He went a step further and installed a toggle switch between the credit switch solder tabs. Then it could be changed between free play and pay to play at the flip of a switch.

I don't have any concern for pay to play so the jumper is the more durable way to set free play over adjusting the credit switches. It just takes a bit more time to implement.

I have been putting switches in mine as of late.
Free play & Chimes on/off. Mounted neatly up front, easy to access thru coin door.
switches (resized).JPG

... Also sometimes add a tilt switch too, for stuck balls or if I want to get some aggressive play in.
IMG_9402 (Medium) (resized).JPG

How about a switch thats easily accessible?

IMG_0135 (resized).JPG

i has a game like that, someone cut a hole the size of a switch box and wired a light switch to it right in the side of the head. talk about going the extra mile.

I had one like that, too! A light switch installed in an electrical box mounted on the side of the game. And it was on a somewhat rare late 1940s woodrail, too - yikes.

i think mine was on a bank a ball (65)
the biggest hole i ever had to fill

Diamond Jack above, did manage to plug hole and repaint game

Is that the correct order or incorrect?