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.