Gottlieb Duotron 1974 Credit Issue Question

I have a Gottlieb Duotron EM Pinball machine from 1974. I've owned it since 1980. I bought it at a local auction here in Minneapolis, MN. The game works properly, I have the manual, schematic and the supplement coin chute circuit diagram which shows different coin chute uses for different parts of the world. I've cleaned and lubricated it as needed over the years I've owned it.

My game came set up as 25 cents for two games. The game has 2 coin chutes and they are set up to mirror each other. I had 2 25 cent coin mechs in the game. I've been using it this way since I got it, but now I'd like to be able to set it up so that coin chute one (left coin chute) is one game for 10 cents and the other coin chute is 3 games for 25 cents. There appears to be options for this as I've set the first coin chute to one coin so any coin that goes into the first chute starts a game. I've set the second coin chute to 3 plays and that works properly. I installed the proper plastic coin slots so a dime and only a dime will fit into the first coin slot and installed a 10 cent coin mech for the left coin slot.

When a quarter is inserted into the right coin slot, the game gives 3 credits. If you press the start game switch the game resets, shoots out a ball and is ready to play. All is good.

When a dime is inserted in the left coin slot it starts a game as if the start game switch was pressed, which is fine, but if you insert another dime it does not give a credit. The main motor cycles and the play field lights go off and then back on but no credit is issued. Is there a way that the first coin slot can give one credit for each coin, or even better, start a game when the first coin is inserted but then when a second coin and subsequent coin is inserted, add one credit for each coin?

This machine is in my basement with 5 other games and a Seeburg V200 jukebox. All my coin operated games take coins and I have a drawer of coins for this purpose.

I can solder as I've changed the capacitors on the Jukebox and other vintage toys. I've also replaced transistors on my solid state games I have a VOM and can check voltage, I'm not great at reading schematics though I have them all for this game. I've attached pictures showing the game, how the coin slots look now and the inside of the game where the settings for the coin switches are.

Thanks in advance for your help.

Game Pic (resized).jpg

Coin slots (resized).jpg

Coin Settings (resized).jpg

#2 6 years ago

???

currieddog

Pinside member

I think it would involve rewiring to make it like the 2nd chute adj. What happens if you move the 1st chute plug into the upper "2nd chute adj", or is that not an option?

#3 6 years ago

rolf_martin_062

Inactive member

Hi Jeffpaletz
welcome to pinside. I live in Switzerland / Europe - TWO-Player-Pins are extremely rare over here - I have not seen (yet) the inside of such an pin. I show on Big Brave:
We toggle-on the pin - (if not plunged then) QB-Game-Over-Relay and ZB-First-Ball-Relay in the Control-Bank plunge / actuate --- "see my green A and B" --- this makes the switch on ZB-Relay (green B) to move to "other than drawn in the schematics !!!". In some way we start a game - the S-Start-Relay (green C) pulls-in (does a lot and) closes its switch (green C) - the SB2-Reset-Control (and more stuff) moves / actuates (green D) ... all the resetting now happens - at the end of the Start-up / Reset: The huge Control-Bank is resetted - among other "QB- and ZB- and SB2- RESET" - important for us: "Switch on ZB (green E) is moved(byy resetting the Bank) to 'as shown in the schematics' ". The first ball is kicked-out - the pin is ready to play an ONE-Player-Game.

We then start --- the S-Relay pulls-in - NOW through switch on ZB-Relay: PB-2nd-Player-Relay (green F) in the Control-Bank does actuate - the pin is ready to play a TWO-Player-Game.

I do not know --- I would like to have an Switch OPEN when PB-Relay is actuated (green G) - because I would like to make the Coin-Lock-out-Coil*** quit pulling.

Coin-Lock-out-Coil*** pulling means: Coins are accepted to fall through the Coin-Switch - to fall into the cash-box.
Coin-Lock-out-Coil*** non-pulling means: Thrown-in coins are not accepted - are reflected - fall into Coin-Return-Compatement.

For "real discussion" we must look at schematics and coin-schematics "Duotron", greetings Rolf

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#4 6 years ago

rolf_martin_062

Inactive member

Hi Jeffpaletz
I like most of my post-3 --- I do not like the last paragraph (about green G) --- FURTHER thinking would be needed. If we'd only add this switch (green D): Once we have played an TWO-Player-Game: We then could not throw-in coins anymore ... (((further thinking needed)))
Greetings Rolf

Added over 6 years ago: addendum: please always read "green G".

#5 6 years ago

???

jeffpaletz

Pinside+ Frequent

Quoted from currieddog:
I think it would involve rewiring to make it like the 2nd chute adj. What happens if you move the 1st chute plug into the upper "2nd chute adj", or is that not an option?

Until recently I ran both coin chutes as 2 plays for 25 cents. The 1st chute plug was in the upper socket. In that position the first coin slot duplicates the settings of the second coin slot.

Rolf, I didn't understand your post.

#6 6 years ago

HOW

HowardR

Pinside member

OP
Quoted from jeffpaletz:
When a dime is inserted in the left coin slot it starts a game as if the start game switch was pressed, which is fine, but if you insert another dime it does not give a credit. The main motor cycles and the play field lights go off and then back on but no credit is issued. Is there a way that the first coin slot can give one credit for each coin, or even better, start a game when the first coin is inserted but then when a second coin and subsequent coin is inserted, add one credit for each coin?

Sounds like a switch is dirty or out of adjustment. Staples will scan your schematic for $2, or Kinkos for $6.

#7 6 years ago

???

currieddog

Pinside member

OP
Quoted from jeffpaletz:
Until recently I ran both coin chutes as 2 plays for 25 cents. The 1st chute plug was in the upper socket. In that position the first coin slot duplicates the settings of the second coin slot.

So, I believe the only thing you could do, as is, is move the plug back and get 3 credits for a dime. If you want what you describe above you'll have to do some rewiring.

#8 6 years ago

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jeffpaletz

Pinside+ Frequent

Any idea what wiring changes would need to be done?

#9 6 years ago

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currieddog

Pinside member

Not quite certain. Can you get the schematic scanned and posted?

#10 6 years ago

rolf_martin_062

Inactive member

Hi jeffpaletz
I do not have the schematics "Duotron" --- I do have an schematics "Big Brave" - there I see "pressing the Replay-Button" starts a new game (resetting included) for one player. Then pressing the Replay-Button starts for second Player. There I also see "having the first coin-chute in position '1 coin - 1 play' ": Throwing-in first coin starts a new game (resetting included) for one player. Then throwing-in a second coin starts for second Player.

From Your post-1 I do not understand if Your Duotron does function like an Big Brave (see description above) --- please write about. IF (if, if) it does function: We then can look at "coining up ONE Reply by throing-in a coin". Greetings Rolf

#11 6 years ago

WOZ

woz

Pinside member

14y 77,050 1,866

As rolf_martin_062 suggests the second dime should add the 2nd player (not a credit). jeffpaletz please confirm whether the 2nd player is being added when you drop the second dime in the left coin slot.

#12 6 years ago

???

jeffpaletz

Pinside+ Frequent

Adding a second dime does not add a second player. It causes the motor to cycle but nothing else changes. I'll work on getting the schematic scanned.

#13 6 years ago

rolf_martin_062

Inactive member

Hi jeffpaletz
can You start for 2nd player by pressing the Replay-Button ?
See the JPG in post-3 --- on the right are the numbers on the schematics. Area 17 / 16 shows the S-Relay and the V-Relay and the Coin Chute and Adj-Plug. Area 13 shows the actuating of PB-Second-Player-Relay, area-11 the ZB-Relay and QB-Relay.
Cameras on mobile phones usually make pictures in JPG- or maybe PNG-Format --- and You can upload such pictures here in pinside. THESE areas on Duotron we woukd like to see. Greetings Rolf

#14 6 years ago

???

currieddog

Pinside member

Quoted from currieddog:
So, I believe the only thing you could do, as is, is move the plug back and get 3 credits for a dime. If you want what you describe above you'll have to do some rewiring.

I think the "mirror" thing threw me off, jeffpaletz, it should be giving a credit as is. Switch somewhere needs adj/cleaning.

#15 6 years ago

HOW

HowardR

Pinside member

Quoted from currieddog:
... Switch somewhere needs adj/cleaning.

Somebody has a sense of humor. Thanks for the laugh, currieddog !

On further reflection, I agree with currieddog . See my post above
https://pinside.com/pinball/forum/topic/gottlieb-duotron-1974-credit-issue-question#post-4245425

#16 6 years ago

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currieddog

Pinside member

Quoted from HowardR:
On further reflection

Badda bing, Howard!

#17 6 years ago

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jeffpaletz

Pinside+ Frequent

To to clarify, you believe it's a dirty switch or that I need to do some rewiring if I want it to add a credit when a second dime is inserted? Please let me know.

#18 6 years ago

HOW

HowardR

Pinside member

OP
Quoted from jeffpaletz:
To to clarify, you believe it's a dirty switch or that I need to do some rewiring if I want it to add a credit when a second dime is inserted? Please let me know.

Quoted from HowardR:
Sounds like a switch is dirty or out of adjustment. Staples will scan your schematic for $2, or Kinkos for $6.

#19 6 years ago

???

jeffpaletz

Pinside+ Frequent

I sprayed contact cleaner on the main bank of contacts that are rotated by the motor. I also carefully read the manual and the explanation of what happens when the first coin slot is set to one coin. According to the manual, putting a coin in slot one starts a game. Putting another coin into coin slot one adds the second player. This is how the game is working now. I suspect it was working that way before I sprayed the contacts because the only thing that changes is that both the 1 and 2 player light in the middle of the back glass and I suspect I missed it. If you put a third coin in the first coin slot the motor cycles and nothing changed, no credit is given. Since in real life use on location once you put in a dime or two there would be no reason to put in more money. The way Rolf Martin (above) explained how the game is supposed to work is in fact how it works.

Other games I've seen add credits when coins are inserted and then you press a start button to start playing. Gottlieb is different than what I am used to.

Thank you all for your help. My pinball machine is working as it is supposed to.

#20 6 years ago

HOW

HowardR

Pinside member

OP
Quoted from jeffpaletz:
I sprayed contact cleaner on the main bank of contacts that are rotated by the motor.

Even if that fixed it, that was a mistake.

#21 6 years ago

???

currieddog

Pinside member

Great that it's fixed, but best not to use that method again. http://www.pinrepair.com/em/index1.htm#lube

#22 6 years ago

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jeffpaletz

Pinside+ Frequent

Thank you for the link. I will never use contact cleaner on my machines again. By the way, about 15 years ago I was using contact cleaner on a friend's game and I turned it on before the contact cleaner had a chance to evaporate. A fire started and did burn off the insulation of the wire. I had to rewire the game completely. It was a ton of work but I did get the game working properly.

Now when I do use contact cleaner I wait for it to dry before turning on the device. I will now be using it less often and not on pinball machines. All 6 of my pinball machines work great and I don't want to harm them. Besides this one I have Capt. Fantastic, Electra, Star Trek TNG, Twilight Zone and Indiana Jones. I take pride in them and clean and change the rubbers as needed.

The contact cleaner is dry now. Is there anything I should do to try and remove it or prevent damage?

#23 6 years ago

rolf_martin_062

Inactive member

Hi jeffpaletz
great - You could fix the fault and have Your pin fully running - as the manufacturer made it: A dime thrown-in starts a game - a quarter thrown-in adds credits to the Replay-Counter - maybe 2 or then 3 or 4 or 5 (adjustable). I hope You say "will live with this".

You can "hope for luck" and try what I show in the first JPG --- unplug the "1st. Coin Chute Adj- Plug" - have it unplugged - set an permanent jumper "like my brown wiring" --- then try the fisrt coin Chute --- big question: Does the coin falling through closes the coin chute switch long enough in time so the Replay-Counter does make an step ?
IF (if, if) "Yes": No need to read the rest of this post.
IF (if, if) "No":

A while ago there was a topic +/- "a coin thrown-in shall add ONE credit to the Replay-Counter using the regular wiring - 5,4,3,2 - but new: 1 replay added". I take an JPG I showed there - freshened-up a bit --- see here )2nd JPG): On top of the JPG is the Adj-Plug for 5,4,3,2 credits to add-up. Throwing-in a coin in the 2nd-Coin-Chute makes the W-Relay to pull-in - it stays pulling, it makes the motor to do a turn of 120 degrees. Within this turn the Motor-1A (marked red) pulses 5 times - along "my red lines" the Replay-Counter is stepped.
IF the Adj-Plug is plugged-in at "pos-5": ALL five closings of motor-1A (marked red) reach the Replay-Unit.
IF the Adj-Plug is plugged-in at "pos-4": The opening of motor-2C suppresses the functioning of "Motor-1A closing the second time". The same with Adj-Plug plugged-in "at pos-3 or pos-2".

We look in the JPG at "Motor Sequence Chart" and see: "Motor-1D and Motor-1B (marked blue) can do the same as motor-2C, -4B, -4C" --- beeing opening when the motor-1A closes. So we could sneak-in "marked blue" a Switch in the wiring "adding credits" - we then would have the possibility to adjust for 5,4,3,1 replays added for a thrown-in coin.

jeffpaletz - You probably would want "a dime adds ONE credit --- a quarter adds 3,4,5 credits" - to the existing W-Relay You would have to mount an additional LIKE-W-BUT-FIRST-CC-Relay. AND: to sneak-in "motor-1B- or motor-1D-Switch": You would have to mount an added, new switch on the motor on the 1B or 1D position - or use an existing switch but add another added relay.
I would not do such heavy altering / adding wires / switches - maybe relays, greetings Rolf

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#24 6 years ago

???

jeffpaletz

Pinside+ Frequent