Michael Isard Posted December 3, 2020 I have just unpacked my old 7740 to give to my son for Christmas. Everything is working ok but there are minor issues with the controller and I wonder if anyone has advice. The contacts are a little loose where the track wire connects. (I think I remember this problem from 35 years ago.) Is there a recommended fix other than just taping the wire to the controller? The controller is stiff where it rotates to control the voltage. That doesn't matter when using the standard flat throttle, but it makes the fancy throttle handle unusable: I worry the 2x8 plate will break, it takes so much force to move the handle. From what I can see searching the forum, it's very hard to open up the case without damaging it, and I am not optimistic that there's any maintenance I can do without opening the case, but does anyone have any suggestions! Thanks! Share this post Link to post Share on other sites
Reker1000000 Posted December 3, 2020 The stiff controller might be able to be fixed by just continuing to move/turn it, I also got a 7864 recently and the dial was a bit stiff when I received it, but after using it for a couple of weeks it's smooth and easy to turn. I think if the track connection wire isn't having any problems with conducting, you should be fine, I agree that there probably isn't much you can do without opening the casing. Worst comes to worst you can buy a used 7864 or even just the transformer part for $5-10 on BL. Shipping isn't cheap (trust me, I know... running 12v trains in the US isn't easy...) but you can probably get away with it for under $50. Welcome to Eurobricks, and like you, I also run 12v trains in the US. The 7740 isn't cheap... hold onto it! I'm glad the 12v gray era is still alive today. Also, I don't know if you've done any research on voltage converters. But if you haven't, here's the one I purchased and it works great: https://www.amazon.com/PowerBright-Transformer-Countries-Convert-220-240/dp/B000MW83OG/ref=sr_1_3? Good luck! Share this post Link to post Share on other sites
Andy Glascott Posted December 3, 2020 If my memory serves me right from reading a lot of 12vposts on here, if the Lego power unit stops working it can be replaced with pretty much any of the regular model train controllers that give a 12v DC output, probably a lot cheaper than replacing the original, and certainly what I intend to do when one of my 3 remaining ones gives up the ghost. Share this post Link to post Share on other sites
Toastie Posted December 3, 2020 2 hours ago, Andy Glascott said: it can be replaced with pretty much any of the regular model train controllers that give a 12v DC output For sure. It will work. Also, when you don't want to go full blast: The original 9V regulators will work as well. You need to fabricate a 9V -> 12 V cable, but on the 12V side it is pretty much "wire terminals". Best Thorsten Share this post Link to post Share on other sites
Michael Isard Posted December 4, 2020 Thanks very much for the suggestions! For now I will hope that the stiffness goes away by itself. Share this post Link to post Share on other sites
Reker1000000 Posted December 4, 2020 Oh, and the 12v trains actually run at about 16 volts maximum... so you may want to factor that in. 12 volts will give a decent clip but won't be the max speed. I personally don't usually run my trains at max speed because I'd prefer to preserve the contacts for as long as possible. Share this post Link to post Share on other sites
Michael Isard Posted December 5, 2020 I have the motor running well around a track circle now. It started out being tentative but after a half hour of solid running it goes smoothly at a reasonable speed on full voltage. When I try to run it very slowly it "bunny hops" which I assume means that one of the brushes is a little dirtier than the other: the hopping is consistent all the way around the circle so I'm pretty sure the problem is in the motor and not dirty track. From the forums it doesn't look as if it's worth trying to disassemble the motor just to fix this minor issue, but if anyone has tips that might improve the situation, beyond just running the motor, I would be grateful! Share this post Link to post Share on other sites
Andy Glascott Posted December 5, 2020 If I don’t run my trains for a a week or two they do that bunny hop thing, which I think is probably more to do with dust on the track than on the pickups, so I try and remember to run them at least weekly, which is easier when I’m not in the middle of building a layout... I’m assuming you cleaned the track and pickups, but if you didn’t, use isopropyl alcohol and cotton wool, works a treat. Share this post Link to post Share on other sites