I recently acquired a 1974 DUOTRON project game. Overall it is just about complete and appears that none of the wiring has ever been hacked up or modified. None of the fuses are blown and I was able to get it partially working and all the coils and playfield switches seem ok. The biggest problem I see is that someone got carried away with lube and it got all over the contacts for the score motor and on many other contacts. Some of it has completely gummed over some contacts. While I wait for the schematics and othe parts to arrive I want to at least clean off all the old oil and grease so those contacts are dry.

I've read it is bad to use contact cleaner but is that ok to use to get the grease and oil off if it sits for a few days afterwards? It can sit while waiting for parts. What are the best cleaners to use to get all the oil off a score motor assembly? I was thinking about putting some paper towels or rags under it, spray off all the old oil, toss the rags, and thenlet it sit to completely dry.

From there I can use paper strips and the other contact cleaning tools to carefully clean them all.

If there are any guides to getting at all the contacts for the score motor that would help. Some look like a pain to get to.

Thanks in advance for any suggestions.

Thanks for the suggestions so far. I do have some 90 % alcohol and can use that on each contact. I'm just concerned about all the extra oil and grease and how to clear that off since much of it can't be wiped off. I also have some spray VCR head cleaner that isn't supposed to leave any residue. It may help going over the assembly with that first and follow up with the alcohol.

Well after cleaning a ton of crud off the contact on the score motor assembly and most the other relays in the cabinet I was able to get the machine up and running. It seems to play pretty well. Once the manual/schematics come I will verify the rest of it. There are a couple score wheels that stick and the credit wheel arm is gummed up so I have to manually add the credits. But it does play and I could start a game and play 5 balls as it should. Also need to replace some bulbs. Once I get ti working I can clean up the PF, install the new rubber rings, and touch up the cabinet.

I've learned a lot so far and dscovered how to pop out modules and move them for servicing. Helped a lot.

The game was missing the back cover on the head but it doesn't look like that would be hard to make.

That is the one. When I picked it up I heard that some of the people who had asked about it just wanted to part it out. That would have been a shame. My plan is to get it cleaned up as good as possible and working 100 percent again. It is my first EM machine and wanted this one for the robot theme and to learn in.

This evening I made more progress. There is a step up step down unit under the PF. It was not working. The grease on the smaller levels to engage the rachet had dried and they were stiff to move. The springs couldn't pull them back in place. Cleaned up that assembly and the bonus by the captive ball started working.

Replaced more bulbs and put a few selective Non super bright frosted leds in the game. Bulbs were missing for the eyes and behind Duotron. Used red leds for the eyes and white under Duotron. Also put a red led under the red insert by the flippers. Still has the classic look of bulbs where you see them but those leds look great when thoughtfully placed.

When cleaning out the cabinet I found a contact arm that was broken off. I'm not sure if that was a leftover piece from one that was replaced or if there is one off the I need to find and replace. Once the schematics arrive I can start checking them all. I also found an odd shaped paper clip. It had been used on the playfield gate. Since that was missing I reinstalled that homemade piece and adjusted it so that works too. I'd like to see if someone with a Duotron can get a Hires picture of their gate assembly and maybe I can make a better one using music wire.

The power cord is scary by I bought a new replacement and will install that soon.

Robert

The 10 point chimes works, the 100 point chime is intermittent, and the 1000 point chime doesn't work at all. Found That the relays in the head control the chimes. They looked ok but found that the chime for 1000 points has a burned up coil. I'll replace that and keep going till I get all working

The plunger tip was also melted on the 1000 point coil. Got some parts from a friend today and cleaned up that whole unit. Now all the chime are working and the 10 and 100 chimes work as they should.

The 1000 point chime will work if I manually actuate the L relay in the head. However if I hit either of the 1000 point targets when lit I don't get the 1000 point score or that chime. It seems that the L relay isn't being turned on. That is the next troubleshooting challenge.

Anyone have suggestions on what to check? I'll see if I can at least measure the voltage across the coil to see if it should be working and just have a bad relay coil. That doesn't look bad but I'll test it anyway.

I was able to get that last chime working today and have a temporary fix on it. One was user error (me) and the other was a real issue. Apparently it isn't supposed to score when special is lit...

When the special wasn't lit I could see the L relay working but no chime. Apparently the chime contacts are pretty burned up and when that happened it also melted a notch in the piece that the relay pulls down to move the contact. As a result it doesn't move the contact enough.

Here is a picture of the relay with the contact that is no longer working as it should. It must have been hot and melted part of the plastic so it doesn't move it as much as it should. I've got it working at the moment but plan on replacing the plastic piece and the set od contacts for the chime that are worn.

ChimeRelay (resized).jpg

I also replaced some of the bulbs with LED's but did so selectively and did NOT use any Super Bright LED's. I used the regular frosted versions. 6 green under the A, B, and C green inserts, 3 red under the red inserts, 2 red for the Duotron eyes, and 2 yellow for Duotron name. All the visible bulbs are still regular bulbs. I'm happy with the results and the machine looks like it should and not some purple abomination that I've often seen on other games.

While playing it this evening I noticed that it wasn't showing the play # in play. I found that two short wires had broken loose on the stepper unit in the backbox for keeping track of the ball. Once I manually made the connection they displayed again. Just need to resolder those and it will be fixed too.

DuotronPlayfield (resized).jpg

I have one remaining issue to track down. During gameplay I can see the bonus properly count up as the captured ball is hit and the hole and switches for add bonus are actuated. The problem is at the end of ball. It counts down as it should but I don't hear chimes or get score for it. At one point I started hearing faint chimes during the countdown and think the score worked and that made me realize that it should probably have been doing it all along. It is probably just another dirty relay contact that I missed or need to go over again. I spent at least 4 evenings just cleaning relays since someone got oil on many contacts. Could have a broken wire on a solder connection as well.

Is anyone familiar with the way that bonus unit is supposed to work and how it would interact with the scoring at end of ball? Not sure if it is on the bonus unit, a relay on the bottom of cabinet, or one in the backbox. I do have the schematics and am reviewing those but any pointers to narrow the search or specific relays to check could save me a lot of time.

Thank you