15th position switch is in line with the J Relay Coil (Add Replay Unit Relay)

Ignore the arrows; special was not working, and I found a bad connection or broken wire between the table (DX contact) and back-box (15th position contact / J contact), so I've got a jumper in there until I spend the time to isolate the problem. So I happened to have this image ready.

I'm poking around with my replay unit, it was set up for 10 replays max when I got it, and looks like the mechanical stuff / 15th position contact is a bit messed up / mangled, so poking around back there is one of my back burner projects.
Specials Problem (resized).jpg

So now *I* am officially flummoxed by the 15th position relay / replay unit stepper on my Duotron.

Primary Symptom: the Replay Unit Stepper never stops, just keeps incrementing, past the stop (whether set for 10 or 15) until the little post mashes into the switches. No damage so far. I've checked the 15th pos switch - it opens properly (actually on the 14th position, needs a little adjustment)

The game decrements fine to zero (there seems to be a mechanical stop there). The game increments properly up through the max, via replay button, special, match, or point awards.

Looking at the schematic I uploaded two posts up the thread; the 15th Pos "Replay" unit N/C switch is in line with the Special Targets. And I've verified that this works - with the replay stepper at max, the contacts open, the special no longer works - the Relay J N/O contacts which lead to the Add "Relay" Unit coil remain open.

HOWEVER, I can continue to add games via the coin chute, points, and match. There seems to be nothing in line with the coil of the Add "Replay" Unit to disable these other paths.

Am I missing something?

Or....is this a wiring error, and I ought to rewire the N/C 15th Pos "Replay" unit to the coil of the Add "Replay" Unit (like in the Big Brave schematic above).

Time to get the soldering iron out. I'm normally loathe to mess with the original wiring but I cannot see how this is not a wiring error.

Edit: Rewire completed. Mischief managed, that resolved things. I'll post a marked up schematic in a bit. I'm just a little sad that the game is no longer "stock" (whatever that means). But glad this annoying little issue is off the punch list. Also glad I could find my soldering iron.

Thanks everyone. Saved me some grief / burning out the J Relay....I disabled the specials for the short term until I come up with Plan B.

I'm not 100% convinced there is a design error, but I see no other provision to inhibit excessive credits via the coin slot, points awards, or matches (just through the special). I too find it somewhat incredible that, if this is an error, it's been out there 45 years. Anyone who can set me straight if I'm off in the wilderness, please chime in!

To help me understand the coils / relays better, I initially assumed there was no problem holding in the J relay coil (like the AX / BX / CX / DX coils, A-9740) - would it be OK to hold in the A-9735 J coil for the duration of the ball (assuming there was some way to clear it) or is this coil rated / intended for short-term / instantaneous duty only?

This is the fun part, right?

Not home at the moment; that component is there but looks to be something less than structural - bakelite or heavy cardstock or light fibreboard. I'll take a photo.

When I got the machine, the pin was at the 10 game setting, the credit unit had run past 15, and the pin had mashed up the limit switches, which is why the 15th position switch needed some attention, it was all bent and crushed.

I thought there might be some sort of a mechanical lock-out (like at the zero position) that was not working or needed some attention, initially.

I'm close to putting things back to "normal" whatever that is and just not running the credit reel up that high. I might need to set the award levels higher, because I hit 3x replays on points pretty regularly!

But just knowing that it's working as designed (and not something worn, broken, or misadjusted) means I can take it off my punch list of little projects.

Here's what I have, a bakelite leaf instead of the silver metal. Much more bendy. Shown here run off the reel (15+) but yeah, hitting the Add Replay Relay does not seem to be messing things up too much. It was all bound up when I got it, so maybe someone really ran it up.

I undid all the "repairs" and back to original state. I upped the score award levels, and will just leave it be as is. Apologies for the fire drill.
IMG_7319 (resized).jpg

So freaking helpful. Perfect really. THANK YOU!