Athearn GP38-2 help

[Anonymous]

I have an Athearn GP38-2 lettered for the BNSF and i wanted to convert it to DCC. So i took it to my local hobby shop and i bought a decoder and everything. I removed the little metal strap thing that bridges some electrical gap to install the decoder. I didn't install the decoder because i found out that an Athearn loco needs a special decoder (don't worry i have another use for the decoder i bought), so i put the strap thing back on, and now it won't run on DC!!! Please help!

[Anonymous]

I'd guess that the metal strip across the top of the motor isn't making good contact with the inverted metal "L" coming up from the trucks. If you can, I'd advise replacing the strip with fine wire soldered in its place. This gives better pickup as it can't move and lose the contact. In the short term, you should be able to bend the ends of the metal strip up so that it presses firmly on the underside of the inverted "L" on each truck.

Fitting DCC to Athearn should be easy enough - you need to remove the strip, then unclip the motor from the frame. Underneath is a small brass clip that passes power through the frame to the motor - remove this and the motor should be isolated, though it's a good idea to double-check with a cheap mulitmeter to avoid letting the smoke out of your decoder! The only possible problem is that some Athearn locos do draw quite a lot of amps, though when I checked a few of mine recently I got very little over 1 amp stall current. Hope this helps!

(Edited to add something I forgot the first time - bit about multimeters!)

[nslakediv]

or the brush spring fell out when you took the metal clip off.

[Anonymous]

Thanks for your advice. I'm going to try that when i get the right decoder.

[brothaslide]

QUOTE: Originally posted by csxguy

. . .i found out that an Athearn loco needs a special decoder. . .

Good info - why do Athearn engines need a special decoder?

[RedLeader]

Actually, they don't need a special decoder, you can fit any decoder made for HO engines as long as it fits in the hood and you know how to wire it, since Athearn's BBs have a frame contact motor, this can be very difficult and many things can go wrong. Digitrax has a couple of decoders designed specially to resolve this problem (AT). They have special harness for easy installment in Athearn BB locos.

There is an article in the October 2004 MR issue describing how to install decoders into Athearn diesel engines, great article and easy to follow (better than digitrax's manual). It took me about 30min for my first SD45-2 to be upgraded, after that it took me about 5-10min for each BB engine retrofiting.

[Anonymous]

Hey, thanks for the correction. My hobby dealer told me that they needed a special decoder for it. I'll look at the magazine.

[RedLeader]

It's not the decoder what's special is the wiring. Athearn BB weren't desiged to host decoders. Many new locos have special sockets to just plug in the decoder. BBs doesn't have this and you must wire it in. So maybe I just expressed myself wrong, you may need a "special" decoder for this, one that have all the wires and harness needed to redirect electricity into the decoder and then sending it form the decoder into the motor. Any worng wiring here and you may be wathcing how 25 bucks turn into smoke.

[Anonymous]

QUOTE: Originally posted by csxguy

Hey, thanks for the correction. My hobby dealer told me that they needed a special decoder for it. I'll look at the magazine.

You dont need a special decoder. A special wiring harness simplifies installation but that isn't needed either as long as you be sure to insulate EVERYTHING from the frame. And dont even try to get power pickup from the place where the motor contacts. You can't solder there. Put that wire to the light post after you take the light off (you cant wire up the stock athearn light or it will blow your decoder as soon as you put it on the track). Other than those two spots it's pretty straightforward.

[bogp40]

Before you go too far, remove that bronze strap again and see if the brush spring is there. If not look around for it. I believe you lost it during first disassembly. If you turned the loco upside down without the clip installed, you may have also lost the brush as well.
When you do get the engine to run again then try installing the decoder. The bronze clip that you removed, the motor has one on top and one on the bottom. To decoder the Athearn you have to isolate the motor from the frame. Pull the motor up off the frame, the bottom motor clip has grounding prongs- they make contact w/ the frame. I always switch the clips- while off solder short 6" wire leads to them. A few pieces of electrical tape is needed to insulate any motor clip contact to the frame. Follow the directions for the decoder as to the wiring. The rail pick up is the metal tab over each truck. If the loco direction is wrong for headlight operation just switch the motor leads. A good trick while working on any Athearn is to install plastic strip over to motor/and flywheels(about 3"" long) this gives you a place to attach the decoder and keep wiring away from the flywheels. I fasten the strip in place w/ RTV silicone or Goo.
Bob K.

[NZRMac]

Hey Guys is this the same model you are talking about?




If so any hints for running wires thru the shell so they don't rub on the flywheels?
I've fitted a soundtraxx decoder to it.


Cheers Ken.

[bogp40]

Ken,
Read my previous reply. Once decoder is wired and tested, glue the strip to the top of the motor. Hot glue gun works great to secure wiring but tape the decoder in place.
Bob K.

QUOTE: Originally posted by NZRMac

Hey Guys is this the same model you are talking about?




If so any hints for running wires thru the shell so they don't rub on the flywheels?
I've fitted a soundtraxx decoder to it.


Cheers Ken.

[Anonymous]

I've found one very useful substance for fixing decoders in place - blutack (sp?). Simple roll a small lump between your fingers to warm and soften it, place it on the frame, and press the decoder onto it. Lenz supply sticky foam pads with their decoders, though as Bachmann don't I felt that this would be a good substitute. Hope this is of use to someone!