Adding Decoders to Older Ahtearns

[Anonymous]

We recently orderd our Digitrax Chief II Radio Control DCC System with an additional booster suply and an additional DT-300R controller. We also ordered some DH121 decoders (1.5 amp; we were told these would work good with the Athearn Locomotives we had). The problem is that we don't quite understand how to install them. We've read that the motor must isolated from the chassis. We performed the 'hard wire' performance tips listed in teh Athearn Locomotives book from teh RAILMODEL Journal. We hard wired the top of the motor to the pick-up tab on the trucks and the bottom of the motor (after we removed an insulated the bottom tab of the lower brush holder from the chassis) was then hard wired to the chassis (as shown in that book). Besides inserting the decoder and wiring it, what else will we need to do. The motor, with the bottom brush holder wired to the chassis, obviously isn't truely isolated from the frame. The way the power is transmitted throught the Athearn trucks, we don't know how to do this. Do we need to replace the trucks? Are we missing something or making a mountain out of a mole hill? Most of these locomotives have Kadee #5 couplers mounted (and height checked with the Kadee coupler guage) to the frame. After reading some other articles, we did go ahead and order some DH121AT decoders too. We'll now have 4 DH121's and 2 DH121AT decoders. We live about 2 hours from any Model Railraod Store, and my work hours currently do not allow much a chance on getting to any of these stores in the near future to buy any books or any parts. If any one can help us (my 14-year old son and I) it would be greatly appreciated. I've already downloaded the manuals, but could find nothing about specifically installing decoders in these locomotives. We want to do it right and not damage anything. We're both anxious to get going as soon as all the stuff arrives. Just figured I'd get an early start on getting information on an area where I already see potential concerns.

thanks

[pgrayless]

Mark,

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Mark,

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Mark,

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Mark,

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Mark,

[pgrayless]

Mike,
Since I also have a copy of the same book, here's my answer. The motor is already isolated from the frame with the exception of the wire that connects the motor to the frame. You should have already removed the small prongs from the bottom motor brush clip and placed electrical tape or something similar between the bottom of the motor and the frame to isolate them from each other. The wire added to between the bottom motor brush clip and the fram was to improve the electrical path between the two, as the small prongs previously removed can be unreliable. This is also true for the connection to the top motor brush clip. By using a wire attached to the trucks and the clip, the preformance is greatly improved. Now all you need to do is to cut both wires in two, and insert the docoder between the cut ends of the wires. All that really matters is to attach the grey and orange wires correctly (sorry, I've installed a decoder in a while, but the instructions should help here). It doesn't matter which side you connect the red and black wires, but I normally connect the black to the frame. Be consistent, as its a good practice to avoid possible problems latter. If you can find a copy, March or April 98 issue of Model Railroader had an article on how to do this kind of install. I followed it exactly, and everything worked fine. Basically, you've already done the hard part.

Paul Grayless
[e-mail]

[Anonymous]

Paul, I will be doing the same thing here in a few months time (I still am in the benchwork phase). But I have 3 Athearn locomotives I bought in 1985. They have never been run since I did not have room for a layout at the time, but now I do.

I was at the National Model RR show in San Jose in July 2000, and a modeler there told me that current decoders would not work on 1985 Athearns, that I needed later models (made after 1990). Is that true? Do I have to buy new motors, etc for these loco's? Is there any way to install them with DCC? Thanks for any suggestions.

John

[greendiamond]

Digitrax makes solderless wiring harnesses which simplify installation of decoders into Athearn locomotives. The information about decoders not working in older Athearns is absolutely erroneous. Athearn upgraded the motors in most of their line in the past decade. These motor draw less current (amps) when running. The older Athearn motors could draw 1.5 to 2 amps per unit. As with any decoder installation, you should check the "stall current" of the locomotive prior to deciding which decoder to used as different decoders are rated by the current they are able to handle. "Stall Current" is the amount of amperage your locomotive will draw when you set your DC voltage to 12V and hold the locomotive down until the wheels stop turning. Then read the current with an amp meter. OK enough for the technical stuff. If you have Athearn locos older that 10 - 15 years, you will be safer to purchase decoders that can handle 1.5 to 2 amps. Eventhough they are more expensive to purchase than cheaper decoders, you are hedging you bets that they won't fry. On the newer Athearn you can feel confident using 1 amp decoders.

Mike Tyl
DCC Dealer and Installer

[Anonymous]

Thanks, Michael, for the accurate information. I am more assured now I can buy decoders and get my 15 year old Athearns running on DCC.