Hi EM folks! Mikala was kind enough to point me in this direction.

Two weeks ago, I started a thread in the "Restorations Documented" section chronicling the restoration and repair of my Duotron . (https://pinside.com/pinball/forum/topic/duotron-1974-or-how-i-learned-to-stop-worrying-and-love-the-relays)

To summarize what is in that thread as of 2/6/2019:
It mostly worked when I purchased it 10 years ago.
I spent several years rehabbing the damage to the case.
As time went on, things started to work less and less well.
About 2 years ago, I put the machine in storage in my parent's basement while we moved. When it went in to storage, it did not work. Player 2's score would not stop resetting.
Now, I am cleaning the machine and learning how to troubleshoot. Pinrepair.com's EM repair guide is open on my tablet constantly while working.
I have recently finished rehabbing the score reels for Player 1. They actually cycle smoothly now!
The anti-cheat switch on the door is pretty mangled. I'm going to order a new one.
I've begun bulb replacement. I've already swapped out 27 of the 95 with LEDs. I'd like to do the whole game after seeing how much of a difference it makes.
Many of the bulb sockets are a bit dodgy. I will be taking Pinrepair.com's advice on how to fix many of them.
Neither inserting a coin nor pushing the start button triggered the "S" relay. It's supposed to lock in via its own switch and a motor 2B switch. Time to check the motor 2B switch.
When tripped manually, the motor cycles one position. At this point, a relay on the motor is supposed to actuate the "SB2" relay and the total play meter. Neither happens. When I manually trip the "SB2" relay, the motor begins running and will not stop. I'm going to check how much voltage is making it to the "SB2" relay coil.
While the motor is running, the first player unit is supposed to reset to zero. I already have it set to zero. It doesn't move. I think I've located the P3 switch stack on motor 1A & 4A. 1A looks good. 4A looks not quite right. the contacts that I have circled never actually touch and are filthy.

I've met some very helpful people over in the "Restorations" area, but still have a ton of EM specific questions. I'll be numbering each question to hopefully make them easier to respond to.

Question 1:

When I test the transformer, I get good voltage in, but the outputs are 5.2V and 21.3V instead of 6V and 25V. How much of a problem is this?

Would a Gottlieb B-10904 match the specs well enough to work? (There's one on ebay for a pretty decent price.)

Cleaned off the leads on the transformer. Now I'm getting 5.8V and 24.8V output. I'll call this fixed.

Also... ouch. Stabbed by exposed wires on those leads.

Question 2:
Motor switch 1A looks awfully funky and possibly damaged? Is it normal for a lifter to look like this?

IMG_20190130_111713 (resized).jpgIMG_20190130_111719 (resized).jpgIMG_20190130_111721 (resized).jpg

Marking this as answered. That is definitely melted and I will be rebuilding that switch stack.

Approximately 115V. The contact points are fairly dirty and oxidized. Tonight, I'll be cleaning them.

Question 3:
Looking at the schematic, it looks to me like all of the relays should be on the 25V line. Every one of them shows 6V on the meter. The only 25V connections that I have been able to find have been to a bump sensor on the floor of the cabinet, a fuse, and motor switch 4C.

Am I reading the diagram that incorrectly or has someone seriously messed up the wiring of this table?

25v line schematic (resized).jpg

This is indeed motor 1A. I've had a hard time observing this switch in action due to its placement. Even seeing the colors on the wires has been a challenge due to the amount of dirt and other stuff in the cabinet. I'll verify the colors later tonight.

After taking this picture, I cleaned all of the contacts with a Flexstone file. I then wiped them down with alcohol where possible.

Side note: Since starting this project, I've gone through half a bottle of Isopropyl alcohol already.

This is what I get for running two threads.

The switches that I think you're referring to are motor 4A.

I think that lifter has got to go. The dirt / whatever was so ground in and the exposure to heat caused it to actually feel metallic.

I want to order complete replacements for motor 1A and motor 4A, but I'm not conversant enough to tell him which part number I need to order from the chart below. I'll call him at lunch today and see if he can walk me through the order.

Motor switches (resized).JPG

Question 4:
Tore down Motor 1 today in preparation for rebuilding Motor 1A. (Motor 1A has a thoroughly mangled / melted lifter and a cracked separator.) Each switch stack was carefully removed from the motor housing and labeled. Some 6-32 nuts are keeping each stack together.
Motor 1 switches separated and labelled (resized).jpg

Naturally, I came across a problem. One of wires had broken away from wherever it was attached. The solder point had snapped off. I desperately need some help on figuring out where this originally went.
Motor 1A Broken Solder (resized).jpg

Rather than dwell on this problem, I finished building a diagram of how Motor 1A was assembled.
Motor 1A Diagram (resized).JPG

I really could use some help identifying where this wire goes.

I do have the manual. Both the original (now basically falling apart) and a replacement that I ordered from Marco's (reprinted with PBR's permission). I'm just not entirely sure what I'm looking at. (Extreme newb)

Can you let me know if I'm reading this right, please? This wire connects to the second switch on motor 1A. That means it triggers "Adds player unit" and would explain why pushing the start button doesn't do anything, right?

If I cross reference with the schematic, that means it's probably actually "slate-white" not a misidentified pseudo green and should go to motor 2C, right?
Schematic - Add player unit section (resized).jpg

The wire is 1 1/2 inches in length. It's such a clean break that I haven't been able to locate exactly where it came from.

Thanks for the help, Rolf!

#duotron is the 2-player version of Magnotron . Almost everything is identical.

I traced the slate / white back to relay "P". I get good continuity on it. The green / white is definitely the one the is broken off. (It's really difficult to tell the colors underneath the years of dirt and dross.) The schematic says that should go to "P3E", I think. What is "P3E"?

There are notations of Pxx all over the schematics, that I just don't understand.

I'll be sure to check that as soon as I get these switch stack rebuilt.

You can ignore that line.

Thanks for the link! I had not found this site.

You are understanding me perfectly. As you were typing this, I was responding to Rolf...

I traced the slate / white back to relay "P". I get good continuity on it. The green / white is definitely the one the is broken off. (It's really difficult to tell the colors underneath the years of dirt and dross.) The schematic says that should go to "P3E", I think. What is "P3E"?

There are notations of Pxx all over the schematics, that I just don't understand.

OK... Mystery of the "Pxx" notation is solved. It refers to the player unit cam switches. I should've been a bit quicker to catch on to that.

Cam positions (resized).jpg

Doesn't explain the floating wire on motor 1A second switch, yet.

Thanks everyone for your suggestions! Been a busy few days. Decent length post coming either tonight or tomorrow...

First PBR order placed.

Here's the current (pun intended) scoop on the wiring.

Parts have been ordered to completely rebuild Motor 1A. I'd replace just the broken pieces (lifter, contact, & separator) but I get the different elements apart. They appear to have either been glued together or have fused together over the years.

Some other parts and spares were included in the order, mostly minor playfield replacement items. The only other operational component's that I ordered were the front door anti-cheat switch and the cabinet bounce switch as both are pretty mangled.

Trying to trace the wires via continuity testing has met with limited success. Closed switches passing the current along to other wires makes it a dicey business. Tracing the wires by hand is a bear because they have them wound so tightly in the bundles.

rolf_martin_062 : that diagram is very helpful. I'm trying to use that and my own testing to isolate where the wire needs to be connected. I think that I was able to identify 2 of the connections that you have drawn above. They are short wires with brown, plastic insulation on them.

Below you will find my wire tracings so far...

Motor 1A - switch 1 (Reset score units) to Motor 1C - switch 1 (Motor runout)
Other wire color on same blade: Red with white boxes
Other connections with same wire: Relays "U", "O", "W", "S", "A", "H", "E", "R", & "SB2"
Conclusion: That should be the Motor 1A in 14 and Motor 1C in area 16

Motor 1A - switch 3 (Scoring) to Motor 1C - switch 5 (Opens circuits to playboard contracts)
Other wire color on same blade: White
Other connections with same wire: Relay "QB" and Motor 2B - switch 2
Conclusion: That should be the Motor 1A and Motor 1C in area 8

Motor 1A - switch 2 (Adds player unit) to ???
Other wire color on same blade: Slate / white ?
Other connections with same wire: Relay "SB2"
Conclusions: This almost has to be the Motor 1A in area 15

I don't understand why you have two Motor 1C's connected in area 17 of the schematic.

Motor 1A has been partially rebuilt. It only required one blade to be rebuilt and 2 replacement separators.Rebuilt Motor 1A (resized).jpg

I'm still tracing the mysterious wires coming from P3E in the hope of finding where the mysterious broken wire on Motor 1A came from. I've had to unbind the wrapping around the wire bundle that leads to the light cabinet. Rebinding the cables with modern cable ties.Light cabinet wire bundle (resized).jpg

My back is aching something fierce from hunching over the cabinet for tonight's work. I loosely wrapped a wire tie around the two wires I'm tracing. That should make it a little easier to pick up my work tomorrow.Wires from P3E (resized).jpg

@rolf_martin_062 & @damoib

OK... I had to carefully remove the wire bundle wrapping down the entire center of the cabinet, but I finished the trace. (I carefully wrapped each intersection made with the wire wrap with brand new wire ties as I went.) It was the only way to be sure I was tracing the correct wire as the alligator clip kept bridging connections and falling off.
Wire bundle (resized).jpg

P3E's inside blade has a cable that runs directly to Motor 1A switch 2 inside blade. P3E's inside blade is also connected to P4E's inside blade. P4E inside blade (resized).jpg

I did a continuity test off that connector to the player 1 10's unit and got tone on two places) a normally closed switch and 2) connector 4 on the printed circuit board.
P1 10's unit - normally closed switch (resized).jpg
P1 10s unit - Connected to 4 (resized).jpg

I'll confirm which one is the direct connection tomorrow. Everything is bundled too tightly to do a conclusive visual trace and my back is killing me from being bent over into the cabinet.

That's an idea I hadn't considered.

It sure does look YEL/GR doesn't it...

It's not. It's actually WH+GR. Once I got further down into the wire bundle, the nasty yellowing wasn't present. It seems to be another symptom of the smoke exposure.

I'll clarify with pictures where the other wires go in a few minutes.

DaMoib

Hopefully this clears it up for you:
Player Unit Switches (resized).jpg

The one that looks YEL+GR Is actually WH+GR. That's part of why I had trouble tracing it. Here's a picture of where it goes into the bar connector:
P3E to right bar connector to Motor 1A switch 2 (resized).jpg

The white is very bright indeed where the wire was in the center of the main bundle.

Machine powered off
Unplugged machine
Control bank reset manually
Plugged machine back in
Toggled power back on.
Relays QB and ZB immediately actuated.

What next?

Already had the "First coin chute adjustment" set to "1 coin 1 play". Dropping a coin in or manually triggering coin chute switch does nothing.

Manually triggering the "S" relay does the following:
1) Starts the motor spinning. It doesn't stop.
2) The under playfield stepper continually counts down even though it is at it's minimum setting.
3) "Total play meter" increments.

What I can see that doesn't happen:
1)The replay unit does not subtract a credit.
2) The "Tilt" light remains on. (The tilt light turns off is the "First coin chute adjustment" is set to "1 coin 2 plays")
3) Player 1 score does not reset.
4) Ball kicker does not activate.

Just a quick note... Thanks to everyone for their help and support. I've been a little tied up as my wife and 2 boys have been trading being sick for the last 3 weeks. Somehow, I've stayed well, but I haven't had any time for pinball work.

I'll be back just as soon as I can.

Thanks to everyone for their patience and indulgence. My boys and wife are all feeling much better! I also had a business trip to Atlanta that put a stop to the work on #duotron

I spent a little more time cleaning contacts and the P1 1000's score reel. The reel needs new springs, but works much better.

ZB activates as soon as I power on the cabinet and stays on when I start the machine.

I'm getting slightly inconsistent behavior on SB2. It activates when I push the power button. The motor cycles for 2 1/3 rotations then stops. At this point, SB2 disengages.

If a ball is on the kickout, the motor will then resume spinning, but do nothing else as far as I can see.

If I remove the ball from the kickout, the tilt light comes on and stays on. The flippers will not actuate and nothing scores.

On ZB, it appears that the 3-bladed switch operates as you describe.

SB2 activates when I press the start button.

If there is no ball in the kick-out, the motor turns 2 1/3 times. During this time, I can hear the stepper in the scoring cabinet moving. Then relay U (Control Bank Reset) will actuate. SB2 releases and the tilt light comes on.

If there is a ball in the return, the motor turns 2 1/3 times, then relay U (Control Bank Reset) will actuate. The motor will continue running. I can watch relay O attempt to actuate, but the kick-out will not fire. The motor will continue to run until I manually press the switches on the right side of SB2.

Please note: This is what happens when I press the start button or actuate the S relay. Dropping a coin in the left (P1) slot triggers a somewhat different reaction that I will document shortly.

Hi Rolf!

SB2 and LB plunge, but not PB.

It is subtracting credits now if I press the start button, but not when I actuate relay S. Addition of credits from the other coin slot is working... mostly. Sometimes only one credit is added when it should be adding 2. No doubt, I need to clean up the action on the credits reel.

Actuating the left (P1) coin slot has a somewhat different reaction that I will document shortly.

OK

More entertaining news! Sometimes, a partial reset of the score reels will happen, but it will not complete.

Those headaches are shared. I've been leaving it on "One Coin - One Play" since writing that message. No sense trying to complicate the troubleshooting.

OK

This is no longer happening. *sigh*

Yes it does.

No it does not.

The tilt light only goes off if I hold in the H relay with my hand. Play field lights flicker when I'm holding this in. Do you think there might be some bad / dirty connections in the H relay?

I don't think so. It's hard to say as it's difficult to cleanly actuate relay H.

It steps down and stops.