Atlas DCC U25B Locomotives

in2tech Oct 6, 2021

  1. freddy_fo

    freddy_fo TrainBoard Member

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    Can you post a pic of the chassis?
     
  2. in2tech

    in2tech TrainBoard Member

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    [​IMG]
    [​IMG]
    There it is.


    Sent from my iPhone using Tapatalk
     
  3. in2tech

    in2tech TrainBoard Member

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    [​IMG]


    Sent from my iPhone using Tapatalk
     
  4. freddy_fo

    freddy_fo TrainBoard Member

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    If you put the decoder board in place and without assembling the other side of the frame can you visually verify the the motor contacts are touching their respective pads on the board? If so then reassemble but also check those motor contacts are not touching any part of the frame. They should only touch their respective pad and no place else. I can't tell for sure from the pics but it almost looks as if that top spring could touch the frame when it's compressed.
     
  5. in2tech

    in2tech TrainBoard Member

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    I'm gonna look at the OLD motor and may even try it in there, as it works, just makes noise and see! Kind of hard to see once it is assembled! Guess I just have to mess with it.
     
  6. freddy_fo

    freddy_fo TrainBoard Member

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    One thing I do whenever I disassemble that type of chassis is tape up the part of the frame where the motor contacts pass by to prevent accidental shorting. Sometimes with new motors the contacts aren't bent at the same place or slightly different length that can create a shorting issue.

    Pic shows one of my locos where I did this. I looped the tape completely around and overlapped on the outside with cut strips of electrical tape.

    20211026_191905[1].jpg
     
  7. MK

    MK TrainBoard Member

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    Kapton tape would have been a better choice. Thinner, doesn't become gooey and high dielectric. Given how little space there is between the frame and shell, thinner is better.
     
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  8. freddy_fo

    freddy_fo TrainBoard Member

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    I did that back before I knew what kapton tape was lol.
     
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  9. in2tech

    in2tech TrainBoard Member

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    Yeah I put it back together and NO short, but it won't work except the lights for now. I am done with this project for now. Maybe later, I'll have to throw in the old motor that doesn't work, one of the other decoders. I hope it isn't the decoder now? I have 2 U25B's running, one quiet, one with noise. The intermountain running like a charm, and also the VO-1000 now since I fixed it. And a brand new CB&Q set arrives Friday. I'll just have to be down a locomotive. I was down two anyway before this. Thought the motor's would fix them, but it's becoming clear, not as easy as I thought?

    Too frustrated right now, and will just cause more issues if I continue this project for now!

    Time to go work on more mock-ups on the layout. No electricity involved there :) Just cutting out the grass sheet.

    I'm going to play now :)
     
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  10. tehachapifan

    tehachapifan TrainBoard Member

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    I see a potential other problem in the pics that MK alluded to earlier, that's probably not related to your current issue. One of the bearing blocks is not orientated the same as the others and the may not have the exact same dimensions on all sides, which could possibly lead to something not aligning correctly. Also, It appears with those particular bearing blocks that there is a channel on two sides and not on the other two sides, unless I'm misinterpreting the photos. This channel, as I understand it, is for the little fingers on the frame halves to slide into and hold the bearing blocks in place. It appears that 3 blocks are orientated so that the fingers are not in a channel. On some other Atlas locos I believe there is a channel on all 4 sides of the bearing block making it a little harder to know which way it's supposed to be orientated, especially if you forget to take note of how they were upon disassembly or if they were previously installed incorrectly.

    ...I also see that a contact strip has slipped off the truck contact in the photo with the chassis assembled (I now see that's not your chassis but the point is still valid). Get a couple of these mal-aligned along with slightly dirty track and/or wheels and you can have no power.
     
    Last edited: Oct 27, 2021
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  11. in2tech

    in2tech TrainBoard Member

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    I swear I have had these things taken apart no joke at least 20 times between the 3 of them, and never had a problem but noise, which I did not know was the motors till recently. Not looking too good for wiring up my layout DCC in multiple places. Better delay that project for awhile :) I know I am not the only one that has had frustrating things happen. I feel bad for all of us.
     
  12. in2tech

    in2tech TrainBoard Member

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    Unfortunately I need photos when you start talking about such things? Don't know all the terminology just yet. I do know I have taken these exact locomotives apart many, many times, BUT, it was month's ago. Because I don't do this as often as some others here. And each locomotive can be a little different in it's own way, I struggle with this type of thing.

    Although thanks to the help here, like the VO-1000, I eventually figure it out. Or break stuff!
     
    Last edited: Oct 27, 2021
  13. Carl Sowell

    Carl Sowell TrainBoard Supporter

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    i2T,

    You probably do not need anymore comments, BUT;

    always use Kapton tape on the chassis points where the motor contacts and decoder tabs meet regardless of what type the connections are. You say the motor will not run, does your power pack or dcc system indicate a short. If the motor tabs or springs, whatever, are not making contact with the decoder tabs then place a dab of solder on the motor tab to build it up a tad. Work quickly so you do not ruin the brushes.

    Next I need to ask you about something that I think my 81 year old eyes are seeing. I have enlarged my screen image to 120% and also used one humping large magnifying glass. The last two images you posted, one with you holding the 1/2 chassis, and the one above it something does not look right. Now it may be me but I see what may be a u-joint that is way out of line with the axle shaft. Check it out.

    Not being critical, just trying to help, be well,
    Carl
     
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  14. tehachapifan

    tehachapifan TrainBoard Member

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    [​IMG]

    What I've circled are the bearing blocks I mentioned. If you look closely, you will see one of them is orientated so that the chassis fingers are in the channel (bottom), while the other one is orientated so the fingers are not in a channel (top), or so it appears in the photo anyway. This may or may not necessarily cause problems, but I suspect something may become mal-aligned an/or the frame halves might possibly not seat together correctly or as tightly as they should. Be careful not to lose the tiny nylon washer(s) when you manipulate the worm/bearing block assembly.

    ....all this said, the whole issue of bearing block orientation is a bit unclear, as it seems some Atlas locos have channels on all sides of the bearing blocks but some seem to come orientated with the smooth side facing out and others with the more faceted-looking side facing out. Nonetheless, having the orientation of the bearing blocks all being the same in a given loco is probably a good idea.
     
    Last edited: Oct 27, 2021
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  15. in2tech

    in2tech TrainBoard Member

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    I enjoy the comments here as that is what eventually helped get my VO-1000 working almost perfect as far as I am concerned. And I noticed those error's too and eventually fixed them. I did finally busted out the BIG arse lighted ( big to me anyway ) magnifying glass and it has helped a lot. That's when I noticed the motor tabs touching the sides of the casing ( once again term(s) ) and causing the short I had at one time. Fixed it, still no motor working. And YES I checked each of the Brand New motors with DC to make sure they worked. I put it back together, it did not work again, except lights, and it was time to put the shell on and set this sucker aside for now :)

    I'll come back to it probably in the next few days, maybe! Been enjoying mocking up my layout, and need to get the L, from the garage, been in there for month's, lay some very basic long ( well for my two 2'x4' bases), to get ready to run a Brand NEW Kato DCC CB&Q Zephyr Set coming Friday! My very first brand new DCC locomotive or set! Everything else from Swap Meet over years, and one used ( VO-1000 ) recently from Hobby Shop locally.

    I really appreciate everyone's help here! I'm not giving up, just taking a break from this project! Man, I hope I did not blow another decoder? Although that one was years ago.

    Thanks everyone!
     
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  16. mtntrainman

    mtntrainman TrainBoard Supporter

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    I will add from my experience ....those bearing blocks are a PITA ! I have had NEW locomotives that the blocks on one end had the block orientations askew from from each other on the same shaft. One block with the flat side up and the other on the same shaft had the grooved end facing up. o_O

    Putting parts back in and making the blocks all look identical in the channel doesnt always work and I have had some locomotives make noise (or worse) after putting them back together. Taking them apart again and flipping those blocks around one at a time hoping to hit the right combination is a fools errand !!!:whistle:

    I found a solution that has worked for me. When I take a NEW locomotive apart...I use a #11 blade and make a light 'score' line in the plastic block the same direction as the shaft...before romoving the shaft and blocks from the frame !!!!(y)

    When putting things back together I make sure those 'score marks' are facing up on each block....regardless of my mind saying they should be identically oriented. This being a working theory that the locomotive ran great 'out of the box' when I first got it new..JMO

    (y)
     
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  17. freddy_fo

    freddy_fo TrainBoard Member

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    When you get back to this first tape up the chassis like what I showed in my earlier picture. Kaptan tape is ideal as noted by others. If the motors are tested as working and you can witness good contact with the board when board installed but before frames halves are joined and lights are on with track power then all that is left is the board. Some decoders have protection circuits that prevent shorts from damaging them but others aren't as sophisticated and possible the motor output circuit is no bueno if an output was shorted to the chassis. Next test is to swap out boards with another loco that has the same chassis if possible. If you are working after that then the board is at issue. Hail mary procedure is to reset the suspect board via CV to factory defaults (procedure should be in the manual) and see if that helps. If after that you aren't able to get things working it's time to consider replacing the decoder.
     
  18. MK

    MK TrainBoard Member

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    Frustration leads to bad decisions so you are wise to take a break from this problem.

    The past few posts contain excellent info. When you get back to it, re-read them and start over.

    We are all cheering for you! (y)
     
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  19. in2tech

    in2tech TrainBoard Member

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    Alright back to the NEW motors for the Atlas U25B's, apparently I blew the decoder on the one I was working on in October this year. Looking for one right now. I'm pretty sure it is an NCE, never bought a decoder before. Any suggestions? And is it indeed a NCE decoder?

    Any info appreciated. Now I am kind of freaked out about replacing the motors if I am gonna fry the decoders. Yeah I know it's all on me, I get it. But this is my First actual attempt at a repair. Still learning!
    In this case I actually have 3 of the same locomotives, which is not usually the case. I could try and put the decoder in a working one, that actually needs one of the NEW motors, and test it, but my fear is causing more damage :) And of course I could use it as an Excuse to Buy a NEW locomotive(s), sad isn't it :) I mean if it Looked fried that would be one thing, but it looks fine, which means nothing I am sure!

    Suggestions, thoughts, any thing? BTW, the little Devil over my shoulder from Animal House is saying BUY new locomotives, in plural :)
     
    Last edited: Dec 17, 2021
  20. freddy_fo

    freddy_fo TrainBoard Member

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    You can swap the decoder other to another loco. The one thing that I'd worry about is the decoder and if that is bad then no need to worry about electrical damage to anything else.

    I suspect those copper tabs from the motor shorted to the frame when you put it all back together. DC that is ok but DCC that is bad because we are feeding track voltage into the DCC electrics via the motor output creating a short situation.

    Before you swap anything around tape up the frame like what I showed previously to help minimize that possibility. Second is when you put it back together try to visually inspect the copper motor tabs that they are contacting the exposed pads on the board you put in there. There should be two square tabs that are offset from each other that have to contact those copper motor leads.

    I've currently a couple of DCC boards I pulled from atlas locos that are yours if you want them. I believe both are lenz decoders.
     
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