LifeLike Proto N GP38-2 erratic operation

Discussion in 'FAQs' started by Herc Driver, Aug 7, 2007.

  1. Herc Driver

    Herc Driver Active Member

    Hi Guys - maybe someone could help me out with this one...

    I've got a new LL GP38-2 low nose, standard DC operation that will run at a low power pack speed, but with an increase in power, stalls out and stops. All the wheels are correctly set per gauge standards, all the copper pickup wires are correctly placed over the touch-point on the truck, the lights illuminate in fwd and reverse like they should. I removed the shell and found that although the frame is tightly secured, if I apply pressure to the bottom of the frame halves (where the fuel tank is modeled) the diesel springs to life and runs fine. This one has me baffled...I've never had a problem running this one before - although it is only a few months old - and the track runs every other diesel fine, so I don't think it's a track issue. Anyone else experienced this one? It is oiled, and all this occurs without pulling a load of cars. Just seems strange that with an increase of power - the engine dies, and applying pressure to the lower section brings it back to life.

    Any ideas will surely help.
  2. woodone

    woodone Member

    I am going to take a wild guess here. Could it be when you increse power, the motor torque is twisting the motor in the motor bracket and causing the copper strips from the brush holder to loose contact,To the frame,when you squeeze the halfs together it makes contact. That is what I would look for. Might try putting a small piece of plastic or wood (tooth pick) betwen the contact strip and the frame.
    Happy hunnting.
    BTW let us know what you find, if you do get it running the way you like.
  3. Herc Driver

    Herc Driver Active Member

    Very interesting idea...I'll have to give it a try.

    I can't see any superficial reason why there would be a loss of motor power - not complete loss of electric conduction since the running lights are still illuminated when the motor quits. I cleaned the track just to make sure that isn't a contributor to the problem...replaced the shell and as before, it will run at lower power settings and if increased very very slowly, it will run at almost full power (something I don't normally ever do with any of my engines). But quick applications of power from crawling speed to medium speed will stop the motor's turning movement, and when I back off the power a bit, sometimes the motor starts moving again without hesitation. This one still has me stumped. The frame is firmly tight, all the electrical pickup points are where they are supposed to be and the wheels are making good contact with the metal strips above the wheel sets. Weird.
  4. doctorwayne

    doctorwayne Active Member

    I not very familiar with N scale locos, but I'm assuming that your loco has a split-frame set-up. Is the motor secure in its mounting? If you squeeze the bottom of the frame, this would have the effect of very slightly parting the frame halves at the top - is there any chance that a very thin shim between the halves of the frame, at the top, would help? Without seeing it, it's difficult to visualise what might be binding. When a motor runs, the motor itself tends to torque in the opposite direction of the rotation of the armature, and this is most noticeable on sudden accelaeration. Still, I'm uncertain as to how squeezing the lower frame remedies the problem. Another reason for a motor to "lock-up" is excessive endplay, either of the armature (causing the brushes to "catch" on the windings) or of the drive train (resulting in couplings hitting things, such as the frame, that they wouldn't normally touch).
    Sorry that I can't be of more assistance.

  5. woodone

    woodone Member

    With the split frame ( It does have a split frame-right?) The contacts from the wheels makes contact with two side contacts, one on each side of the loco, this contact is pressed into the frame. That is what makes the two split halfs have power. One + one -. the motor is mounted in a plastic holder, witch insulates it from the the frame halfs.
    On the motor there are two copper contacts contected to the motor brushes. These copper contacts make contact with the frame one on each side. I am thinking one of these copper contacts loosing contact with one of the frame halfs when it is powerd up. The light will stay on because you have power to the frame halfs, it is the motor the is giving you fits.:curse:
    Let us know what you find- share the good news:thumb:
  6. Herc Driver

    Herc Driver Active Member

    Good information - thank you guys! I'm going to try to open the split frame up (not too hard, just loosening and removing the screws) and see if I can determine where the motor is having problems. To me, the problem seems to be only with the motor so I'm going to pay close attention to the pickup points and if they maintain correct contact with the motor (thanks woodone) and look at the motor to drive shaft connections to make sure there's no binding (thanks Wayne).

    But this little project will have to wait for a couple of days...unfortunately I've got too many other things to do first.

    Thanks very much for the great ideas - at least I now have some key areas to start looking. Once I get it running right - I'll post the how's and why's of what I found out.
  7. woodone

    woodone Member

    OK Herc Driver--- What did you find-- its been a day or so to get her fixed- any luck in finding what is going on.:confused:
    I am just giving you a bad timesign1

    But let us know what you found OK:thumb:
  8. Herc Driver

    Herc Driver Active Member

    No worries...

    My apologies for not finding anything out yet...I've been flying a lot this week in the mighty Herc and truely haven't had the time to dive into the engine's problem. Ironically, I ran this engine's running mate - another GP38-2 of the same LifeLike lot and it runs at about the same speed as the problem engine - but without the sudden stopping. So at least I have one to compare to the other (and a "master" to rebuild the problem diesel from if I can't figure out where all the pieces go once I take it all apart).

    I will (soon I hope) figure this thing out and post what I find just in case others run into this might take a while though.
  9. diesel

    diesel Member

    Although these are great troubleshooting tips... Proto has a warrantee you will enjoy that Kato and Atlas do not: ie forever. The more you take it apart the less they will honor the warrantee. Protos tech guy is Jerry in the service dept. (HO anyway, think he does N too though) Call him and explain the problem. Even if you get his voicemail he calls you back pretty quickly and can either assist you on the phone or will tell you to mail it in. I know it's a pain to mail in but sometimes it just makes more time for you to get the rolling stock weathered or whatever.

  10. Herc Driver

    Herc Driver Active Member

    Thanks very much Dan - I haven't had the time to really take it apart and look into the causes/reasons for the erratic operation...but I might just give the Tech guys a try first before winding up with pieces all over the desk. Thanks.
  11. Herc Driver

    Herc Driver Active Member

    Hi guys...I know it's been way too long since I revisited this thread...but I finally got around to opening up that GP38-2 unit, and unfortunately, I can't find a thing wrong with it. The motor and gears turn freely with no extra oil or lube near the electrical contact points, the metal electrical contact strips touch the points of the trucks where they're supposed to and the wheel sets turn easily and are gauged correctly. There is no binding of any part. I have no way to test the electrical board to see if a tiny resister or other component has gone bad. The motor will not rotate under electrical power, but both directional lights work as normal. My only alternative is to open up the running mate to this engine and swap motors and see if I can narrow it to the board or motor. I figure, if I can make another motor work in it, it's got to be a bad motor. And if the good motor won't run, the only thing left is a bad electrical board. I could also swap frames just in case that's an issue...but I really don't see how it could be.

    If it's the electrical board, I'll consider writing LifeLike/Walthers to get a replacement board and swap them out, or gut the motor and gearing and have a nice looking dummy engine.

    Any other ideas?
  12. Herc Driver

    Herc Driver Active Member

    Fixed it...go figure.

    After swapping engines and thereby proving the electrical board worked, I reassembled the 38-2 with its original motor and in the process noticed a small metal strip that should pick up power from the right side of the frame was not making contact with the frame. A very gentle bending of the metal - making sure it would touch the frame - and reassembly then back on the test track...and it worked, BUT, not when I put the shell back on. Everytime I reattached the shell, I got an overload signal on the power pack. (Someone explain that one to me.) Took it completely apart again then reassembled it. This time it works and actually works better than it's running mate - the other LL GP38-2. I have no idea why putting the shell back on the unit would cause an went on really easily, no binding or twisting, and the frame was already tightened with the set screws. There's no metal inside the shell that could touch anything except the frame. Oh well...I'm just glad it's running again.
  13. Squidbait

    Squidbait Recovering ALCO-holic


    Somehow, in putting the shell back on, you caused something to short out. That's what gave you the overload indication on your power pack. It may be that that contact you bent was contacting the wrong part of the frame, or something like that.

    Glad to hear you've got it fixed.
  14. Herc Driver

    Herc Driver Active Member

    You could be very right...that little metal piece was bent towards the "middle" of both frame halves. Although I took great care, it could have been touching something it shouldn't have, effectively shorting out the motor.

    I'm not ready to put out a "engine repair" sign just yet. Right now, I'm happy with "dumb luck" and a good running diesel.

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