Joined: 01/12/2023(UTC) Posts: 6 Location: Massachusetts
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Hi! I'm from Massachusetts - resurrecting my childhood Marklin HO train set for my kids and pulled out the old DB 81010 engine. Placed it on the track and when I tried to crank the controller, it did nothing (no lights, no movement). Tried a different engine and it worked fine. Put both engines on the track and neither worked - took the DB 81010 off and the other working engine started to move. Guessing I have a short circuit in the engine, but no clue where to start troubleshooting. Both sides of the wheels AND the center rail all tone when I use a continuity tester and I'm guessing that's not great/causing the short circuit. Any guides on where to look/how to start troubleshooting?
Thanks again, targeting getting this up and running for my kiddos for Christmas!
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 1 user liked this useful post by jekhokie
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Joined: 21/12/2012(UTC) Posts: 1,483 Location: Hrvatska
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You can get advice when you take a picture of the open locomotive from all sides so we can see what could have been?
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Joined: 04/02/2011(UTC) Posts: 3,555 Location: Paris, France
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Hi Jekhookie (A first name would be just great) Thank you for joining our great forum of Märklin friends If we are talking about the BR81 Märklin (3 rails with a slider): - if posed on a 2 rail installation, it will short circuit the rails - if posed on a 3 rail installation and if it creates a short circuit, I suggest to unscrew the slider and check. If can be of the wrong type or it can be improperly mounted: on some type, installing the wrong way, it creates a short Here is a BR81 (3031) seen from bottom with the original slider Notice, it is not symetric (so it may be mounted the wrong way Notice the contact zones under the slider and its Pertinax insulating support. Normally they contact a small PCB to bring the voltage to the motor while the other contact zone is facing a hole. Improperly mounted, the contact zone touches the metal chassis and creates a short  Cheers Jean |
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Joined: 01/12/2023(UTC) Posts: 6 Location: Massachusetts
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Screenshot 2023-12-04 at 12.25.09 PM.png (1,641kb) downloaded 25 time(s).Thanks guys - my name is Justin by the way, and it's a 3-rail track with 3-rail trains. I think you're on to something - I removed the middle slider and put the engine back on the track and while it obviously didn't run, the other engine did in fact run (telling me the middle slider is at least one culprit here). I also ran a continuity test using my multimeter testing both middle rail to wheel (when the middle rail was mounted) and it beeped, telling me that's not good news. I'm attaching pictures of the inside of the engine and the slider. While I see the slider looks the same as the original pictures you posted (minus the fact that it appears to have a separate screw hole for some reason), I'm not sure how this thing would EVER have run like this. To do a final test, I actually slid a piece of paper under the slider on the contact side that WASN'T supposed to touch the metal PCB connector and when I put it on the track, while the engine didn't run, it didn't prevent the other engine on the track from running (no short), so I think that further points to the slider (unless that paper simply stopped the positive voltage from touching the engine, but that the contact plate/slider simply aren't touching or something else is going wrong). Now, the question is - why. I'm wondering if there is a piece of insulation missing from under the slider and/or if the contact of the slider isn't aligning to that gold connection plate for some reason (or entirely the wrong slider)? Thoughts/ideas? Screenshot 2023-12-04 at 12.10.24 PM.png (1,985kb) downloaded 31 time(s). Screenshot 2023-12-04 at 12.10.47 PM.png (2,203kb) downloaded 22 time(s). Screenshot 2023-12-04 at 12.10.31 PM.png (3,001kb) downloaded 24 time(s). Screenshot 2023-12-04 at 12.10.36 PM.png (3,333kb) downloaded 22 time(s). Screenshot 2023-12-04 at 12.10.41 PM.png (3,559kb) downloaded 26 time(s).
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Joined: 01/12/2023(UTC) Posts: 6 Location: Massachusetts
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Continuing to think about this...
I suppose it's possible that the slider tests were a red herring in that removing the slider stops the flow of positive voltage being shorted by the engine itself and the short is elsewhere within the engine (and because the wheels are ground, placing the engine on the track without the slider doesn't create the shorted connection because the positive voltage isn't entering the engine). Now my head is spinning more, trying to think of other ways to narrow down the short.
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Joined: 09/07/2023(UTC) Posts: 39 Location: Delaware, Long Neck
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I don't own a BR81 but I think the body is metal and I know the chassis is metal. You have a lot of wires and connection points on the right side of the engine. If any should touch the metal shell, it will short out. I have had this happen with an early BR38 and I resolved the issue by placing a piece of electrical tape on the inside of the body opposite the soldered electrical connections and my problem was solved.
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Joined: 05/07/2019(UTC) Posts: 48 Location: Rogaland
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Originally Posted by: jekhokie  Continuing to think about this...
I suppose it's possible that the slider tests were a red herring in that removing the slider stops the flow of positive voltage being shorted by the engine itself and the short is elsewhere within the engine (and because the wheels are ground, placing the engine on the track without the slider doesn't create the shorted connection because the positive voltage isn't entering the engine). Now my head is spinning more, trying to think of other ways to narrow down the short. Hello jekhokie !! This is very easy to check.Skrew out the pick up shoe from the lokomotive and test it with the red wire from trafo on the slider and brown wire at the housing or wheels.If it works now its shortcut betveen lokomotive and slider. Best regards kaav800
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Joined: 04/02/2011(UTC) Posts: 3,555 Location: Paris, France
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Hi Justin The slider is the modern equivalent of the old one. The old one had just a longer Pertinax piece (the brown insulator piece) to fit onto metal positioning tabs. I believe your slider was just positionned the wrong way. It is NOT symetrical so one position is good and rotating by half a turn, it is bad. Good or Bad? On your picture we clearly see the slider orientation is bad because the the two contact tongues, instead of touching the contact PCB will touch the frame making a short circuit  Nothing is missing in your loco I think Cheers Jean |
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 3 users liked this useful post by JohnjeanB
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Joined: 01/12/2023(UTC) Posts: 6 Location: Massachusetts
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Thanks everyone - I did in fact try flipping the slide around and trying it that way, although I'll say it looked less correct in that orientation because one of the contacts didn't fall into that cavity area of the bottom of the train (it was touching the frame for sure). Either way, still no luck with the slider in either direction. Any other tips for how to isolate a short? I guess I'm going to need to try and trace the slider contact path and see if I can tone with a multimeter back from there until I find potentially where things are going south.
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Joined: 05/07/2019(UTC) Posts: 48 Location: Rogaland
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Originally Posted by: jekhokie  Thanks everyone - I did in fact try flipping the slide around and trying it that way, although I'll say it looked less correct in that orientation because one of the contacts didn't fall into that cavity area of the bottom of the train (it was touching the frame for sure). Either way, still no luck with the slider in either direction. Any other tips for how to isolate a short? I guess I'm going to need to try and trace the slider contact path and see if I can tone with a multimeter back from there until I find potentially where things are going south. hello jekhokie !! Yes thats a good idea.If thats not bringing any resoults,you have to check the shifter reley (umschalter) in the lokomotive.This loko has telexcouplings so that complicates things a bit. Its spesially the contacts you must check on the top of the reley.Be shure that nothing are in contact with mass.Careful they are very fragile.If this is ok,you scould have to move further to the engine. Good luck ! kaav800
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Joined: 01/12/2023(UTC) Posts: 6 Location: Massachusetts
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Ok thanks everyone, I tinkered a bit more and what I found is when I remove the armature from the stator housing, I noticed the short circuit was no longer present on the track (the other engine did in fact run). However I don’t know if this is also a red herring based on it physically cutting off the electrical path when doing this. Any ideas where I might look next given this data?
I also ended up replacing the motor brushes thinking that was probably a good idea regardless but that obviously had no effect.
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 1 user liked this useful post by jekhokie
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