(Topic ID: 257499)

Duotron - My First Game


By JudeRussell

5 months ago



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#1 5 months ago

I recently picked up a Gottlieb Duotron game from a local amusement shop - mostly working but needs some tweaks. Not particularly attached to this machine but it was the best combination of condition, price, and era they had in the shop.

I'm looking forward to digging in a bit (just received the schematic / manual today, have some spare parts and cosmetic replacements on order). I'm a EE old enough to have played the game back in the day, but not old enough to have spent a ton of time with relay / ladder logic - so I know enough to be dangerous. I'm less concerned about the electrical aspects (that I got covered) as opposed to some of the mechanical work. Most of the places I've worked, the techs did not want the engineers touching the soldering irons. All that being said, I'm pretty sure working on the game is gonna be as enjoyable as playing it.

A quick list of things I've identified as needing attention (nothing urgent) aside from bulbs:

* Lane A lamp flicker and AX relay not pulling in. I pulled out the AX relay and cleaned it up a bit - back in working order. My first victory (not counting adjusting the award levels, which was interesting).

* Special targets not working. The targets score properly with no special, the special light comes on but no special target function. I've traced the proper voltage out of DX relay in the J relay chain but can't find it on the J relay or the replay unit limit switch; might be a broken wire, or something screwy with the Replay unit (limit switch). Not urgent but I do want to get that working.

* Match Light - sometimes (infrequent) there's no match number lighted; I assumed a bad bulb but I've been writing the numbers down and I seem to have seen all of the digits. So....? Nothing mission critical.

* Left and right kickers need a little mechanical adjustment so they expel the ball reliably straight up the lane - the ball gets hung up in the lane too often, resulting in multiple bonus / scores.

* Two player / ball count issue. One player works fine (3 balls, have not tried 5, probably worth switching over just as a data point for troubleshooting) but with two player, the machine stops after the third total ball (i.e. first players 2nd ball). Have not dug in yet but I'm guessing there's a contact / relay problem in the last ball circuit.

Overall, it's not the best playing game out there, but it's good enough to mess around with. I find the captive ball feature is a little too rewarding (I'm thinking of hacking it so it only pays off 3x bonus for 3 ball, rather than 5x, to ratchet up the challenge)

That's enough for now. I'm finding lots of good tips and troubleshooting ideas in the forum, so grateful for all the history recorded here.

#6 5 months ago
Quoted from DaMoib:

Might I also suggest developing some alligator clip/EZ hook jumpering skills? For instance - jumper around the suspect paths in the special award circuit.
http://www.pinrepair.com/em/index3.htm#features
https://pinside.com/pinball/forum/topic/using-schematics-and-8-foot-jumper-wires

Yep. Just this morning ordered some ez-hook probes for my DMM and some longer length jumpers. And a couple of rechargeable worklights...

#7 5 months ago
Quoted from frenchmarky:

Does it do a normal game over with a match number lighting, or not lighting? The latter would likely be the slam tilt circuit or something else forcing it to game over vs. normal end of a game.

One player game works perfectly (in terms of ball count, match, awarding a free game, etc.). Infrequently I see no match numbers lighted but not sure if that's a bad bulb or something else. I'm in the process of playing a lot of games to collect data

Next time I open it up I'll do a bit more research. Want to set it to 5 ball play and see if that works properly (one player) / changes the symptoms (two player).

My best guess right now is the PB relay - because the Player 2 lamp is not lighting (ever) and it's in the Last Ball chain (XB relay) - so if that relay is not engaging properly, it could cause these issues.

I dug around a bit in the Replay Unit last night and that looks like it needs some attention (the 15th Pos contacts were locked open despite no credits on the reel) - so that's likely at least part of the non-working special.

Still, ridiculously easy to score free games on the machine - when I got it, the replay awards were set to the lowest values. One of my first tasks was to set those to the recommended 3 ball values, but even there I won 3 replays on points this morning just messing around / testing.

#9 5 months ago

Spent a bit this evening replacing a few bulbs, replacing the pop bumper caps (were faded out) and, replacing all the rubbers (including the shooter springs / tip and rebound ball). Wow what a difference! Like a whole new game, especially in terms of ball action all over the playfield, but especially up around the pop bumpers.

There were actually a handful of incorrect rubbers installed - mostly 5/16" around posts that should have had a larger ring around 2 posts. But also, the entire captive ball island in the middle - the supplied 4" rubber wraps around the entire thing (including in front of the captive ball), what was on there were 5/16" around most of the posts and a couple of 1 or 1-1/2" rings around the side.

I was concerned / confused by that (the replacement 4" ring makes the captive ball play far differently) and adding to my confusion, there are two playfield images on the main Pinside site, one has the 4" large ring, the other is not 100% like mine was, but close (with no rubber in front of the captive ball). With the new ring, the ball tends to bounce back to the same side it was hit on. Not sure if it's scoring 2x; if so that makes it even easier to score.

There are also two wire pins on left and right side of the captive ball area (one on each exterior side) that look like they might have been installed after the fact, perhaps to contain the ball without the larger ring / rubber.

All in all, a good weeknight project....

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#13 5 months ago
Quoted from frenchmarky:

I fixed up a Magnatron and kept it a while, never knew that ring was supposed to go in front of the balls like that. It is a very weird-looking arrangement for a captive ball, probably why I assumed the captive ball should be 'open' since that's how nearly all of them are on other games.

Yeah, it seems odd to me as well. I'm still not 100% sure - the manual page is here -https://pinside.com/pinball/forum/topic/duotron-rubber-ring-location-chart - and shows a single ring A-10225 (4") but for all I know owners did not like it and standardized on something else. The little metal rods / pins (one of mine is a finishing nail, which adds to the impression it might be an add-on) continue the mystery.

I also found a decent resolution Gottlieb Flyer which clearly shows the ring cutting across the front.

Quoted from fingersport:

I am a fairly good player and I find this game very hard to beat. I left the game the way I got it with the replay scores at something like 75,000 and 84,000 point.

I have the award levels at recommended (much lower) levels mostly for friends / visitors, I'm assuming I'll get pretty solid on the machine once I have it all fixed up.

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#14 5 months ago
Quoted from DaMoib:

Facts aside, I remember the satisfying "clack" of contacting the bonus booster captive ball on a shot... does it make that sound with the ring in the way?

No, in fact it's a little too bouncy, IMHO. The captive ball tends to go back and forth in the trough, ending up on the same side you hit it (and presumably scoring twice). I might have to get some smaller rings and set it up custom - I can throw some of the old rings back on but I like the new bounce. I think there were 2x 1" rings (back left and right diagonals) and the rest single post rings along the front - so you'd lose the side bounce along the left and right verticals. Not sure how that would affect play and action.

#15 5 months ago

Well, the Specials issues is about 80% resolved - poking around with a multi-meter and found ~ 30 Vrms at the Yellow+Blue wires at the Replay Unit as well as the J contact (green arrow), but ~ 15 Vrms at the DX contact (red arrow). Jumpered that and the special works!

I was all set to put it down to a bad solder joint or broken wire, but then recalled that the good voltage was in the head of the machine and the bad voltage in the body and there was a connector in between. I've never had the machine in pieces, it was delivered assembled, so not the first thing in my head.

So that's my first place to look. Have not been able to spend the time to track it down, but with the jumper in place it's all good.

Was a little surprised that the red special does not clear when you actually score a special (it's been a while since I've played one of these older games) but not seeing any path in the relay logic that would clear the AX/BX/CX relays (which close DX and light the special) so I'm guessing it's working correctly.

No luck on the two player thing. I switched over to 5 Ball operation, which works properly in single player mode but only 4 balls per player in two player mode.

But clues:

a) The Double Bonus light is not working in single player or double player mode
b) The 1 or 2 Player lamps does not toggle in two player mode
c) The match replay does not work in two player mode (I've matched Player 1 and Player 2, but no replay advance)

So that ought to get me close in terms of narrowing it down.
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#16 5 months ago

Belay my last. I finally opened up the back and got access to the backglass lamps. A lot were out or loose.

So....the Bonus Light now works properly, the Player 2 light works properly. Two player / 5 ball game it works properly for four balls, then ball moves to launcher (for Player One / Ball Five) but game stops and match light comes on.

I jumpered out the QB contacts as a test - I could play the Player One last ball but once it drained it was over.

Inspired by another thread here I poked around the Player Unit (not as scary as I thought) - the contact seemed to just barely be on the rivets (overshoot) so I loosened the contacts and realigned so they sit square on the rivets. No change. Would that it were that easy. I do want to poke around a bit more to be sure the other wipers are landing properly and making good contact.

But I'm emboldened by my willingness to dig into the steppers - so it's only a matter of time before i figure it out.

#18 5 months ago

Two Player Issue Fixed!

Not a bad bit of troubleshooting - because it got me familiar with the Player Unit (heretofore terrifying, now not so much), the latching relays (which I had not realized were latching) and the Motor (still terrifying, but less so)

I did poke around the player unit and aligned the wipers to the rivets. Not the problem but a good exercise.

Then I spent some time staring at the latching relays, watching the 1st Ball relay (ZB), the Double Bonus relay (LB), the 2nd Player Relay (PB) - all working correctly - as well as the Last Ball relay (XB) and Game Over relay (QB) - which were not working correctly in two player mode. Me sitting on the floor with the coin door open, launching balls and watching relays for a while.

That convinced me that things were looking good in the Player Unit (because the Double Bonus was working as intended, green arrow) so something in the last few contacts before XB (red arrow), specifically the O relay contact (N/O) and the Motor 1C contact (N/C).

I looked at the O relay first (less terrifying) and that was fine, then moved to the motor, and found the contacts were a hot mess. Did not clean them (yet) but dug in with a continuity tester and manually rotated the motor checking for proper function, and tweaked the spacing to make sure they worked properly.

Took me two tries (the first time I accidentally killed the chimes and the ball advance) but with a bit more care and attention to detail, I succeeded.

Problem solved! Thanks for all the ideas. I also found EM Pinball Troubleshooting - Testing Gottlieb Player Units by Kerry Imming (2011) to be super helpful in terms of understanding the sequencing and increasing my comfort working with it all.

Two Player Solve (resized).jpg
1 week later
#19 5 months ago

A very minor update.

Purchased a bag of LED replacement bulbs (warm white, frosted) and went to town. I decided I did NOT like them above the playfield (behind bumpers, etc.) so left those incandescent. I replaced all of the LEDs under the playing field (A / B / C / Special indicators, bonus indicators) and they look fine and also a lot more stable (the incandescents were a bit more prone to less than perfect connections and dimming). Also replaced all the backglass lights with the exception of the Game Over blinking bulb.

Behind the glass they look fine, the score reel lights are a shade too white but I can live with it (less heat, I had a bit of paint burn-through above the Player 2 reels).

I also went picked up some new rings for the center island to replace the 4" big ring (which was too bouncy and did not give that happy little ball-to-ball clack)

Have not tracked down the bad wire noted above (Player 2 issue) but the jumper continues to work fine.

1 week later
#20 4 months ago

The game has been in good shape over the holidays (lots of playing and some friends have been by to visit). I've gone back and forth about the captive ball ring / rubbers and have finally put the "stock" 4" ring back on. My thoughts:

#1) The 4" ring provides a bit more action in the top area (pop bumpers) and side lanes (toward the right/left kicker lanes) - and this game can use all the "pep in its step" that it can find.

#2) The 4" ring, cutting straight across the front behind the captive hole, seems to make it easier to hit the captive hole (angle shots that carom in) and that's perhaps the least active feature on the table, so it brings it into play more regularly.

#3) Even when the captive ball bounces back and forth (due to the rubber bounce) it only seems to score 5x bonus (vs. 10x) so my concerns about making it too easy to score were less of an issue.

One question: Lighting the special targets (via the A/B/C lanes) seems to be a latching thing (for the duration of the ball in play) so you can hit the special multiple times. It seems to be working properly per the schematic (no path to turn the special off). Is this normal for Gottlieb games of this era? For some reason I recall the special going out when you win a game (from memories of my wasted and perhaps a bit fuzzy youth)

I almost want to add some contacts or rewire to unlatch the special and reset the A/B/C lanes if you hit the special, just to make it more interesting. But I don't want to hack the game from the original.

I also have loved games that cycled the lane lights in response to one flipper; that seems like a bit too complex to add in here, but fun.

#22 4 months ago

No adjustable settings for the rollovers - just 3 ball (5x bonus for captive ball) or 5 ball (3x bonus) but everything else is the same.

Everything else is fixed. Just the garden variety points / award adjustments. Hit A + B + C lanes lights 2x special targets, which stay lit for the remainder of the ball regardless of how many wins. In some ways that's been the most challenging way to win (and therefore, my usual focus) - since it's pretty easy to rack up points with a decent ball, especially on the last ball with 2x bonus.

Not sure where that card came from - the instruction set I downloaded from Inkochnito's Pinball Cards are in alignment with the game play and features.

#25 4 months ago

I've had the lanes apart / posts removed (replacing bulbs, plastic guides, rings) and don't remember seeing alternate holes in the surface. But I was not looking for them either.

#31 4 months ago
Quoted from SirScott:

Every time you put LEDs in an EM, God kills a kitten.
[quoted image]

Well, I'm allergic to cats

Seriously, though, until I get in and spend the time to clean up / tighten / replace some of the lamp holders, the incandescent bulbs are a bit more erratic - the LEDs draw so much less current that they stay lit more reliably with marginal connections. I've kept it incandescent up top, dislike the look of the LEDs there.

#32 4 months ago
Quoted from Daditude:

Any pics??
Show it off!

Happy to! Pretty happy with the condition of the playfield / cabinet considering where it was found (a warehouse filled with broken / busted / abandoned pool tables, jukeboxes, and video games).

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#34 4 months ago
Quoted from DaMoib:

Looks like it's in great shape... and shiny!

Well, I have an LED light bar mounted over the playfield for work purposes. I pulled the glass off to take a few pictures, otherwise the glare would be problematic.

#35 4 months ago
Quoted from frenchmarky:

See arrows, if no one ever changed them from the factory on your game you will only see dimple marks, but those are the alternate screw locations.[quoted image][quoted image]

I do see the dimple marks (thanks for the tip!) but I'm pretty sure the factory presets are the more challenging (conservative) positions.

Top lanes, the middle two barriers extend a little higher (default), making it harder to hit the A lane, correct?

Side A/B/C targets, the forward position (default) makes it harder to hit the targets, correct?

Side lanes (I think your arrows are in the wrong place, I'm looking at a divot at the top of the rail separating inner and outer lanes) the lower position for the rail (default) makes it easier to drain to the outside, correct?

1 week later
#38 4 months ago

In the engineering world, this is clearly a case of RTFM (Read the __ing Manual) which I actually have (and did not bother to read), so thanks. Turns out my game is set up conservatively in terms of the posts / lanes, which is fine with me. There are also some divots at the top of the side lanes which confused me.

I ended up picking up a digital level (which gives me something new to obsess over), curious about the incline - was set up close to the manual recommended 3.5° so I cranked it up to 4.5° which makes it play a bit faster (and really helps the pop bumper action at the top of the playfield)

My one minor crank at this point is the side lane kickers which get hung up on the newish (and thicker) lane rubber too often (lots of scoring) - cleaned the contacts in line with the kicker relays, loosened up the posts and held things slightly inward as I retightened (to ever so slightly widen the lanes) and the aforementioned increase in incline - seems to have made things much better. Anything I'm missing? I don't see any way to adjust or re-aim the simple kickers.

Oh, and Mr. Duotron get a sister, just picked up a Domino (which puts me at 100% capacity in my basement office) so I'm messing around with two machines now.

3 weeks later
#40 3 months ago

Long time no post.

Duotron got a flipper coil upgrade today to yellow dots - not really mission critical but my second game (Domino, and yes, this is how it starts) came with upgraded flipper coils and as a result the older game with the 2" flippers had more kick to it; made Duotron feel a bit less engaging. I totally get that the stronger coils could cause some mayhem to plastic parts but there's not a lot to break here (the captive ball behind the ring is not an issue) - no drop targets or ramps or other special features. I also replaced the flipper return springs; the left was very weak which I think contributed to the malaise with the old coils; I replaced both springs just to be consistent.

Any tricks or tips to aligning the flippers? I eyeballed 'em and it took a few tries to get them feeling balanced left / right - I imagine that someone out there has a procedure or alignment tool to take some of the guesswork out of it.

The one thing I am adding to the shopping list is a higher power (probably heat adjustable) soldering iron. I definitely want to redo the coil connections with a better quality joint at some point. They are solid but not pretty and I'd like to clean them up permanently.

I've got a punch list of things needing a little attention, but the game continues to play well and get good use - when people come over they like competing via the two player option. I have come to understand the "not that much going on" opinions about the game, but it has remained a solid first game without too many complicated bits.

#42 3 months ago

Duotron's Yellow Dot flipper coils were a short lived experiment. Yes, the game played hotter and faster and dare I say more fun. But I also hit the glass with the ball more times in a few days than I had in many months; and watched the ball hop over rails a few times - the hotter flippers made it more of a 3D / airborn game and the playfield's not really intended for that. Nothing broken or damaged, but I could envision broken playfield parts, glass, more playfield wear, etc.

What was interesting is how it changed the game - the top of the playfield (pop bumpers, A-B-C lanes, sprecials target) was much more in play, as expected. But it also took away the captive ball shot in some ways - which seems to be more of a finesse shot. Faster / harder, the ball was likely to hit the posts rather than move the captive ball. On the other hand, the center kicker hole was almost too easy - a strong shot hit right at it bounced off the ring behind and plopped right in.

I spent some time optimizing the flippers with the standard A-5141 coils, and after a few hours of working on some issues that cropped up during the coil swap-out - https://pinside.com/pinball/forum/topic/gottlieb-score-motor-stops-just-short-of-normal-stop#post-5469206 - I'm back in business.

#43 3 months ago

A minor post. I've been cranky about the chimes, despite installing a chime rebuild kit a while back.

Turns out the chime plungers were completely gummed up....should have cleaned them when I replaced the coil sleeves. A good alcohol wipe, and for good measure I ran an alcohol damp paper towel down the coil sleeve. Things are singing.

3 weeks later
#44 75 days ago

Duotron got taken apart for a bit as I brought in a Sky Rider that I'm working on for a friend. But that did not last long; I missed playing it and had some little projects to do, so I shoved my desk back another 12" and made room for three pins. And I thought one was gonna be too tight in my little condo basement.

Picked up some Orange Dot coils and installed this afternoon, and definitely hit the sweet spot - a bit more kick to get the ball to the top of the playfield, but not so much that I'm taking it airborn, hitting the glass or hopping over / busting up playfield pieces as I was with yellow dot. We have a winner. So I think I'm done screwing around there for the moment.

Still a couple of minor issues but nothing mission critical.

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