Decoder for Athearn geeps

[CFournier]

This may have been discussed before. Any sugestion on a decoder for non-decoder ready Athearn GP9, GP35 type locos?
Chris

[Anonymous]

Digitrax makes a specific decoder for older Athearn engines. You can plug/clip it onto the engine with no soldering. Check their web site for the specific model number. I don't remember it right now

[rrinker]

DH123AT or the DH163AT, depending on how many functions you want (just lights for the DH123AT, lights plus 4 others with the DH163AT), and if you want back-emf (163) or not (123).

You can also get just the harness seperately to use any 9-pin JST plug decoder.

Or just solder wires to the copper bars yourself and save a few $$. Just remember to remove the little tab on the lower motor brush spring AND insulate the motor from the chassis on the bottom as well - a layer of electrical tape works fine.

[CFournier]

Thank you. I took note of the info and will be looking for the digitrax at a good price.

[Anonymous]

QUOTE: Originally posted by CFournier

Thank you. I took note of the info and will be looking for the digitrax at a good price.

Tony's Train Exchange and Loy's Toys usually have the best prices on deocders (and DCC stuff in general).

http://www.tonystrains.com/
http://www.loystoys.com/

[rwissbaum]

So what is "back EMF" and what does it do? I notice it seems to add to the decoder price.

[ndbprr]

I believe (but may be worng here) that back EMF supplies a reference point back to the decoder to keep the motor spinning at the same rate and therefore the engine at the same speed regardless of hills or other issues. It creates a kind of a cruise control for model railroads.

[rrinker]

That is essentially correct. It can help quite a bit for real slow speed running as well.

Adding back-EMF doesn't ALWAYS drive the decoder price through the roof - check the TCS T-1. I've installed a couple of those now, and have decided the, barring the availability of a direct drop in replacement, such as the Digitrax DH163L0 for Proto2K, I am going to use the TCS T-1 wherever possible. Next to get them wil likely be a few older Athearn locos, and from all user reports I've heard, they make the stock Athearn motor run GREAT.

--Randy

[mcouvillion]

On the Athearn motors, you can swap the position of the upper and lower contact bars so that there are no tabs available to touch the frame at the bottom of the motor. Use a small needle nose pliers to pu***he tabs back from whence they came and use that bar on the top of the motor. Be careful taking the bars off. In addition to holding the motor all together, they hold the springs on the brushes. If you are not careful, the springs can get away from you. They can be a bear to find in the carpet! Solder your wires from the decoder to the bars when they are off the motor. Clean and tin the end of the bar (I usually do the end where the spring will be) before attaching a tinned wire. You can use a small piece of electrical tape as an insulator under the motor (over the bare metal of the frame), but without the tabs there it won't make contact anyway.

Mark C.

[CFournier]

Thanks to all of you.
Chris

[Anonymous]

QUOTE: Originally posted by rrinker


Adding back-EMF doesn't ALWAYS drive the decoder price through the roof - check the TCS T-1. I've installed a couple of those now, and have decided the, barring the availability of a direct drop in replacement, such as the Digitrax DH163L0 for Proto2K, I am going to use the TCS T-1 wherever possible.

I've gotten very fond on the TCS decoders; great value for the money! I tried a T-1 in a Stewart FT, and it works just fine. If I didn't already have a Digitrax DH163P laying around, my other FT would also get a T-1. I also tried their A1X in an older Kato-based Stewart engine, and it works great. And it's cheaper than the Digitrax and NCE equivalents (both of which I've also used). I have a few more old Stewarts to convert, and they're all going to get the TCS A1X decoders.